U.S. patent application number 11/099175 was filed with the patent office on 2005-12-15 for water-resistant vegetable protein adhesive dispersion compositions.
Invention is credited to Frihart, Charles R., Wescott, James M..
Application Number | 20050277733 11/099175 |
Document ID | / |
Family ID | 35150473 |
Filed Date | 2005-12-15 |
United States Patent
Application |
20050277733 |
Kind Code |
A1 |
Wescott, James M. ; et
al. |
December 15, 2005 |
Water-resistant vegetable protein adhesive dispersion
compositions
Abstract
Water-resistant, protein-based adhesive dispersion compositions
and methods for preparing them are provided. The adhesive
dispersions are prepared by copolymerizing a denatured vegetable
protein, such as soy flour, that has been functionalized with
methylol groups with one or more reactive comonomers, and preparing
an acidic dispersion of the adhesive. The adhesive dispersions
exhibit superior water resistance, and can be used to bond wood
substrates, such as panels or laminate, or in the preparation of
composite materials.
Inventors: |
Wescott, James M.;
(Waunakee, WI) ; Frihart, Charles R.; (Dane,
WI) |
Correspondence
Address: |
KNOBBE MARTENS OLSON & BEAR LLP
2040 MAIN STREET
FOURTEENTH FLOOR
IRVINE
CA
92614
US
|
Family ID: |
35150473 |
Appl. No.: |
11/099175 |
Filed: |
April 4, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60560133 |
Apr 6, 2004 |
|
|
|
60562393 |
Apr 15, 2004 |
|
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Current U.S.
Class: |
524/589 ;
524/593 |
Current CPC
Class: |
C08H 1/02 20130101; C09J
4/00 20130101; C09J 189/02 20130101 |
Class at
Publication: |
524/589 ;
524/593 |
International
Class: |
C08K 003/00 |
Goverment Interests
[0002] This work is supported in part by the U.S. Department of
Agriculture Forest Service under Cooperative Research and
Development Agreement No. 02-RD-11111120-116. Accordingly, the U.S.
Government has certain rights in this invention.
Claims
What is claimed is:
1. A method of preparing a protein-based adhesive dispersion, the
method comprising the steps of: denaturing a protein, whereby a
denatured protein is obtained; methylolating the denatured protein
with a formaldehyde source, whereby a methylolated, denatured
protein is obtained; copolymerizing the methylolated denatured
protein with a comonomer under basic conditions to yield a
protein-based adhesive, wherein the comonomer is selected from the
group consisting of phenol, phenol formaldehyde, urea, urea
formaldehyde, melamine, melamine formaldehyde, melamine urea
formaldehyde, and mixtures thereof; and adding an acid to the
protein-based adhesive until a pH of less than 6.0 is attained,
whereby a protein-based adhesive dispersion is obtained.
2. The method of claim 1, further comprising the step of: reacting
the protein-based adhesive with additional formaldehyde under basic
conditions.
3. The method of claim 1, further comprising the step of:
copolymerizing an additional comonomer with the protein-based
adhesive in the adhesive dispersion.
4. The method of claim 3, wherein the additional comonomer
comprises a polymeric methyl diphenyl diisocyanate or a novolak
resin.
5. The method of claim 1, wherein the protein is a component of a
soy flour, wherein the soy flour has a particle size of about 80
mesh or less, and wherein the soy flour comprises from about 0 wt.
% to about 12 wt. % of an oil and from about 30 wt. % to about 100
wt. % of the protein.
6. The method of claim 1, wherein the step of denaturing comprises
the steps of: forming an aqueous, alkaline solution of the protein;
and maintaining the solution at an elevated temperature, whereby a
denatured protein is obtained.
7. The method of claim 1, wherein the step of methylolating is
conducted in a basic solution at a temperature of from about
0.degree. C. to about 100.degree. C.
8. The method of claim 1, wherein the formaldehyde source is
formaldehyde, and wherein a total amount of formaldehyde reacted
comprises from about 20 wt. % to about 30 wt. % of the total
protein content of the flour.
9. The method of claim 1, wherein the adhesive dispersion comprises
from about 10 wt. % to about 99 wt. % of the comonomer.
10. The method of claim 1, further comprising the step of:
preparing a comonomer in the presence of the methylolated,
denatured protein.
11. The method of claim 1, further comprising the steps of:
preparing a comonomer; and blending the comonomer with the
methylolated, denatured protein.
12. The method of claim 1, wherein the adhesive dispersion has a pH
of less than about 6.
13. The method of claim 1, wherein the adhesive dispersion has a
solids content of from about 30 wt. % to about 60 wt. %.
14. The method of claim 1, wherein the adhesive dispersion has a
cured resin water extraction amount of less than about 45%.
15. An adhesive dispersion, the dispersion comprising an acid, the
adhesive comprising the reaction product of a copolymer of a
protein having a plurality of methylol groups and at least one
comonomer.
16. The adhesive dispersion of claim 15, wherein the protein is a
soy protein, and wherein the soy protein is a component of a
soymeal, the soymeal having a soy protein content of from about 40
wt. % to about 50 wt. % and an oil content of less than about 11
wt.
17. The adhesive dispersion of claim 15, wherein the comonomer is a
methylol compound selected from the group consisting of dimethylol
phenol, dimethylol urea, tetramethylol ketone, and trimethylol
melamine.
18. The adhesive dispersion of claim 15, further comprising a
coreacting prepolymer.
19. The adhesive dispersion of claim 18, wherein the coreacting
prepolymer comprises phenol formaldehyde.
20. The adhesive dispersion of claim 15, comprising less than about
2.5 wt. % free phenol and less than about 1 wt. % free
formaldehyde.
Description
RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Application No. 60/560,133, filed Apr. 6, 2004 and U.S. Provisional
Application No. 60/562,393 filed Apr. 15, 2004. All
above-referenced prior applications are incorporated by reference
herein in their entirety and are hereby made a portion of this
specification.
FIELD OF THE INVENTION
[0003] Water-resistant, protein-based adhesive dispersion
compositions and methods for preparing them are provided. The
adhesive dispersions are prepared by copolymerizing a denatured
vegetable protein, such as soy flour, that has been functionalized
with methylol groups with one or more reactive comonomers, and
preparing an acidic dispersion of the adhesive. The adhesive
dispersions exhibit superior water resistance, and can be used to
bond wood substrates, such as panels or laminate, or in the
preparation of composite materials.
BACKGROUND OF THE INVENTION
[0004] Ancient adhesives raw material choices were limited. Starch,
blood, and collagen extracts from animal bones and hides were early
adhesives sources. Later, suitable raw materials used in adhesives
expanded to include milk protein and fish extracts. These early
starch and protein-based adhesives suffered from a number of
drawbacks, including lack of durability and poor water
resistance.
[0005] Adhesives based on protein-containing soy flour first came
into general use during World War I. To obtain suitable soy flour
for use in these early adhesives, some or most of the oil was
removed from soybean, yielding a residual soy meal that was then
subsequently ground into extremely fine soy flour. The soy flour
was then denatured and, to some extent, hydrolyzed to yield
adhesives for wood bonding under dry conditions. However, these
early soybean adhesives suffered from the same drawbacks as other
early protein-based adhesives, and their use was strictly limited
to interior applications.
[0006] In the 1920's, phenol-formaldehyde (PF) and
urea-formaldehyde (UF) adhesive resins were first developed.
Phenol-formaldehyde and, less frequently, modified
urea-formaldehyde resins were exterior-durable, but high raw
materials costs at that time limited their use. World War II
contributed to the rapid development of these adhesives for water
and weather resistant applications, such as exterior applications.
However, the low cost protein-based adhesives, mainly soy-based
adhesives, continued to be used in many interior applications.
[0007] After World War II, the petrochemical industry invested vast
sums of money in research and development to create and expand new
markets for petrochemicals. Within several years, the once costly
raw materials used in manufacturing thermoset adhesives became
inexpensive bulk commodity chemicals. In the 1960's, the price of
petrochemical-based adhesives had dropped substantially, such that
they displaced nearly all of the protein-based adhesives from the
market.
SUMMARY OF THE INVENTION
[0008] It is conventional wisdom that water-soluble adhesives that
retain their water solubility after drying or curing do not offer
the exterior durable properties required in many composite panel
applications, and will wash away from the substrate or undergo
processes involving complex debonding mechanisms. Many of the
petrochemical based adhesives on the market today are initially
water soluble, or at least dispersed in water, and then become
water insoluble after proper conversion into the crosslinked
thermoset.
[0009] Accordingly, a water-soluble adhesive dispersion that also
possesses water durable bonds to inhibit cohesive failure is
desirable.
[0010] Past attempts to combine the soy protein with the
phenol-formaldehyde resins have generally been unsatisfactory in
producing a suitable adhesive that can compete with the standard
phenol-formaldehyde resin in all aspects. For example, some resins
are only suitable for use in two component systems that cure too
quickly to use in making composites. Some resins do not exhibit
satisfactory stability. Other resins do not provide good bond
strength and require high caustic levels that lead to poor moisture
resistance and bond degradation over time. Extra processing steps,
high formaldehyde content of the adhesive, and poor moisture
resistance in the bonded product can also limit the chance of
commercial success. Accordingly, a protein-based adhesive or
adhesive dispersion that exhibits similar performance
characteristics is desirable.
[0011] Over the past several years, the cost of petrochemicals used
as raw materials in thermoset resins has risen to the point where
protein-based adhesives can now compete economically in the same
markets that are today enjoyed by the thermoset adhesives. A
protein-based adhesive dispersion that combines the cost benefits
of a low cost raw material with the superior exterior durability
characteristics of thermoset adhesives is therefore highly
desirable.
[0012] In accordance with the preferred embodiments, a low cost
soybean-based adhesive dispersion suitable for exterior use is
provided. The adhesive dispersions can be prepared using a simple
process. The process involves the denaturization of the soy protein
and the modification and stabilization of the soy protein using
aldehydes, such as formaldehyde. This stable protein can be blended
with a formaldehyde curable resin, such as phenol-formaldehyde,
urea-formaldehyde, or melamine-formaldehyde resin, either at the
adhesive manufacturer's plant or at the adhesive user's plant. The
resulting adhesive is then combined with an acid to yield an acidic
dispersion.
[0013] The adhesive dispersions of preferred embodiments can be
prepared by copolymerizing methylolated, denatured soybean flour
with selected comonomers. Suitable comonomers include those
currently used in thermoset adhesives, such as phenol-formaldehyde,
urea-formaldehyde, and melamine-formaldehyde resin. The cured
adhesives when dispersed in acid offer superior water
resistance.
[0014] Accordingly, in a first embodiment, a method of preparing a
protein-based adhesive dispersion is provided, the method including
the steps of denaturing a protein, whereby a denatured protein is
obtained; methylolating the denatured protein with a formaldehyde
source, whereby a methylolated, denatured protein is obtained;
copolymerizing the methylolated denatured protein with a comonomer
under basic conditions to yield a protein-based adhesive, wherein
the comonomer is selected from the group consisting of phenol,
phenol formaldehyde, urea, urea formaldehyde, melanine, melamine
formaldehyde, melamine urea formaldehyde, and mixtures thereof; and
adding an acid to the protein-based adhesive until a pH of less
than 6.0 is attained, whereby a protein-based adhesive dispersion
is obtained.
[0015] In an aspect of the first embodiment, the method further
includes the step of reacting the protein-based adhesive with
additional formaldehyde under basic conditions.
[0016] In an aspect of the first embodiment, the method further
includes the step of copolymerizing additional comonomer with the
protein-based adhesive in the adhesive dispersion.
[0017] In an aspect of the first embodiment, the additional
comonomer includes a polymeric methyl diphenyl diisocyanate.
[0018] In an aspect of the first embodiment, the additional
comonomer includes a novolak resin.
[0019] In an aspect of the first embodiment, the protein includes a
soy protein.
[0020] In an aspect of the first embodiment, the soy protein
includes a soy flour.
[0021] In an aspect of the first embodiment, the soy flour has a
particle size of about 80 mesh or less.
[0022] In an aspect of the first embodiment, the soy flour includes
from about 0 wt. % to about 12 wt. % of an oil.
[0023] In an aspect of the first embodiment, the soy flour includes
from about 30 wt. % to about 100 wt. % of a protein.
[0024] In an aspect of the first embodiment, the soy flour includes
a soy isolate.
[0025] In an aspect of the first embodiment, denaturing is
conducted in the presence of an alkali.
[0026] In an aspect of the first embodiment, the alkali includes
sodium hydroxide or potassium hydroxide.
[0027] In an aspect of the first embodiment, the method further
includes the steps of forming an aqueous, alkaline solution of the
protein; and maintaining the solution at an elevated temperature,
whereby a denatured protein is obtained.
[0028] In an aspect of the first embodiment, the solution includes
from about 6 to about 20 wt. % sodium hydroxide.
[0029] In an aspect of the first embodiment, denaturing is
conducted for about 48 hours or less and at a temperature of from
about 20.degree. C. to about 140.degree. C.
[0030] In an aspect of the first embodiment, the step of
methylolating is conducted in a basic solution at an elevated
temperature.
[0031] In an aspect of the first embodiment, the formaldehyde
source includes formaldehyde.
[0032] In an aspect of the first embodiment, methylolation is
conducted at a temperature of from about 0.degree. C. to about
100.degree. C. for about 24 hours or less.
[0033] In an aspect of the first embodiment, the step of
copolymerizing is conducted at an elevated temperature.
[0034] In an aspect of the first embodiment, a total amount of
formaldehyde reacted includes from about 20 wt. % to about 30 wt. %
of the total protein content of the flour.
[0035] In an aspect of the first embodiment, the comonomer includes
phenol formaldehyde.
[0036] In an aspect of the first embodiment, the adhesive
dispersion includes from about 10 wt. % to about 99 wt. % of the
comonomer.
[0037] In an aspect of the first embodiment, the method further
includes the step of preparing a comonomer in the presence of the
methylolated, denatured protein.
[0038] In an aspect of the first embodiment, the method further
includes the steps of preparing a comonomer; and thereafter
blending the comonomer with the methylolated, denatured
protein.
[0039] In an aspect of the first embodiment, the method further
includes the step of blending additional comonomer into the
methylolated, denatured protein.
[0040] In an aspect of the first embodiment, the adhesive
dispersion has a pH of less than about 6.
[0041] In an aspect of the first embodiment, the adhesive
dispersion has a solids content of from about 30 wt. % to about 60
wt. %.
[0042] In an aspect of the first embodiment, the adhesive
dispersion has a cured resin water extraction amount of less than
about 45%.
[0043] In an aspect of the first embodiment, the method further
includes the step of adding a component selected from the group
consisting of extenders, fillers, accelerators, catalysts, water,
and mixtures thereof to the adhesive.
[0044] In an aspect of the first embodiment, the acid includes a
mineral acid.
[0045] In an aspect of the first embodiment, the acid includes an
organic acid.
[0046] In an aspect of the first embodiment, the acid includes
sulfuric acid.
[0047] In an aspect of the first embodiment, the acid is selected
from the group consisting of hydrochloric acid, formic acid, acetic
acid, nitric acid, and phosphoric acid.
[0048] In an aspect of the first embodiment, the acid is added to
the adhesive until a pH of from about 4 to about 5 is obtained.
[0049] In an aspect of the first embodiment, about 3.5 parts
sulfuric acid is added per about 100 parts adhesive.
[0050] In an aspect of the first embodiment, the acid is added to
the adhesive at a temperature of from about 0.degree. C. to about
90.degree. C.
[0051] In an aspect of the first embodiment, the method further
includes the step of providing a solid substance; contacting the
solid substance with the adhesive dispersion; and recovering a
composite.
[0052] In an aspect of the first embodiment, the composite includes
a fiberboard.
[0053] In an aspect of the first embodiment, the solid substance
includes an agricultural material.
[0054] In an aspect of the first embodiment, the agricultural
material is selected from the group consisting of corn stalk fiber,
poplar fiber, wood chips, and straw.
[0055] In a second embodiment, an adhesive dispersion is provided
prepared according to a method including the steps of denaturing a
protein, whereby a denatured protein is obtained; methylolating the
denatured protein with a formaldehyde source, whereby a
methylolated, denatured protein is obtained; copolymerizing the
methylolated denatured protein with a comonomer under basic
conditions to yield a protein-based adhesive, wherein the comonomer
is selected from the group consisting of phenol, phenol
formaldehyde, urea, urea formaldehyde, melamine, melamine
formaldehyde, melamine urea formaldehyde, and mixtures thereof; and
adding an acid to the protein-based adhesive until a pH of less
than 6.0 is attained, whereby a protein-based adhesive dispersion
is obtained.
[0056] In a third embodiment, a composite board is provided
including the adhesive dispersion prepared according to a method
including the steps of denaturing a protein, whereby a denatured
protein is obtained; methylolating the denatured protein with a
formaldehyde source, whereby a methylolated, denatured protein is
obtained; copolymerizing the methylolated denatured protein with a
comonomer under basic conditions to yield a protein-based adhesive,
wherein the comonomer is selected from the group consisting of
phenol, phenol formaldehyde, urea, urea formaldehyde, melamine,
melamine formaldehyde, melamine urea formaldehyde, and mixtures
thereof; and adding an acid to the protein-based adhesive until a
pH of less than 6.0 is attained, whereby a protein-based adhesive
dispersion is obtained.
[0057] In an aspect of the third embodiment, the composite board
further includes a material selected from the group consisting of
wood fiber, wood flakes, wood board, wood veneer, and wood
particles.
[0058] In an aspect of the third embodiment, the composite board
further includes a wax.
[0059] In a fourth embodiment, an adhesive dispersion is provided,
the dispersion including an acid, the adhesive including the
reaction product of a copolymer of a vegetable protein having a
plurality of methylol groups and at least one comonomer.
[0060] In an aspect of the fourth embodiment, the adhesive
dispersion further includes at least one coreacting prepolymer.
[0061] In an aspect of the fourth embodiment, the comonomer
includes one or more methylol groups.
[0062] In an aspect of the fourth embodiment, the coreacting
prepolymer includes one or more methylol groups.
[0063] In an aspect of the fourth embodiment, the vegetable protein
includes soy protein.
[0064] In an aspect of the fourth embodiment, the soy protein
includes soy isolate.
[0065] In an aspect of the fourth embodiment, a soymeal having a
protein content of from about 40 wt. % to about 50 wt. % and an oil
content of less than about 11 wt. % includes the soy protein.
[0066] In an aspect of the fourth embodiment, the comonomer is a
methylol compound selected from the group consisting of dimethylol
phenol, dimethylol urea, tetramethylol ketone, and trimethylol
melamine.
[0067] In an aspect of the fourth embodiment, the coreacting
prepolymer includes phenol formaldehyde.
[0068] In a fifth embodiment, an adhesive dispersion is provided,
the dispersion including an acid, the adhesive including the
reaction product of a copolymer of a vegetable protein having a
plurality of methylol groups, and at least one comonomer, wherein
the adhesive includes less than about 2.5 wt. % free phenol and
less than about 1 wt. % free formaldehyde.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0069] The following description and examples illustrate a
preferred embodiment of the present invention in detail. Those of
skill in the art will recognize that there are numerous variations
and modifications of this invention that are encompassed by its
scope. Accordingly, the description of a preferred embodiment
should not be deemed to limit the scope of the present
invention.
[0070] The processes of preferred embodiments involve the
denaturization and stabilization of proteins for use in adhesive
dispersion formulations. The stabilized proteins can be blended
with one or more reactive comonomers, then dispersed in acid prior
to use. The selection of the protein source, its denaturization and
stabilization, and the selection of and reaction with the comonomer
can each contribute to the adhesive's performance.
[0071] The process for preparing durable vegetable protein-based
adhesives from soy flour involves preparing the flour, denaturing
the flour, methylolating the flour, and finally, copolymerizing the
methylolated soy protein with a suitable comonomer, such as phenol
or formaldehyde-modified phenol. Other suitable comonomers include,
for example, urea, melamine, phenol, acetone, and any of their
corresponding methylol derivatives. The adhesives can be prepared
using the methylolated compounds as raw materials, or suitable
compounds can be methylolated via reaction with formaldehyde as a
step in the process of preparing the adhesive.
[0072] The Protein Source
[0073] The process employs a suitable protein source for the
co-polymerization to form adhesive bonds. Protein sources having
high protein contents, such as 40 wt. % or less up to about 100 wt.
%, are generally preferred. Particularly preferred are protein
contents of from about 45 wt. % to about 50, 55, 60, 65, 70, 75,
80, 85, 90, 95, or 100 wt. %. Higher protein content generally
correlates with improved co-polymerization, resulting in the
formation of strong adhesive bonds and good water resistance. While
enriched protein sources are generally preferred, non-enriched
protein sources can also be employed. Accordingly, many biomass
materials with appreciable protein content are suitable for use in
the preferred embodiments.
[0074] While the preferred embodiments refer to soybean flour as
the protein source, other protein sources are also suitable for
use, as will be appreciated by those of skill in the art. Soybean
flour is generally preferred due its low cost and good protein
content. Non-limiting examples of other sources of vegetable
protein include, for example, nuts, seeds, grains, and legumes.
These sources include, but are not limited to, peanuts, almonds,
brazil nuts, cashews, walnuts, pecans, hazel nuts, macadamia nuts,
sunflower seeds, pumpkin seeds, corn, peas, wheat, and the like.
Other sources include protein-containing biomasses, such as waste
sludge, manure, and composted manure. Additional and/or different
processing steps from those described for preparing soymeal can be
used in refining and separating a protein from a raw product of
other protein sources, as will be appreciated by one skilled in the
art. The processed proteins can be employed to produce adhesives
acceptable for various applications.
[0075] Soy flour comprises a hull (8 wt. %), a hypocotyl axis (2
wt. %), and a cotyledon (90 wt. %). The soybean plant belongs to
the legume family. There are typically 2-3 seeds per pod and as
many as 400 pods per plant. The soy flour is prepared by grinding
soy meal. There are several suitable processes for the generation
of soy meal. Soy meal is typically obtained from soybeans by
separating all or a portion of the oil from the soybean, for
example, by solvent extraction, extrusion, and expelling/expansion
methods.
[0076] In solvent extraction methods, soybeans entering the
processing plant are screened to remove damaged beans and foreign
materials, and are then comminuted into flakes. The soybean oil is
removed from the flakes by extraction with a solvent, such as
hexane. While hexane is generally preferred as a solvent, other
suitable solvents or mixtures of solvents can also be employed.
Suitable solvents include hexane, acetone, ethanol, methanol, and
other solvents in which the oil to be extracted is soluble.
Suitable extraction apparatus are well known in the art and can
include, for example, countercurrent extractors. After the defatted
flakes leave the extractor, residual solvent is removed by heat and
vacuum. Soymeal produced by solvent extraction methods contains
essentially no oil (<1 wt. %), from about 50 to about 60 wt. %
protein, and from about 30 to about 35 wt. % carbohydrate.
[0077] In extrusion methods, after the soybeans are screened and
flaked, the flakes are heated under conditions of pressure and
moisture in an extrusion apparatus. Suitable extrusion apparatus
are well known in the art, including, for example, horizontal screw
extrusion devices. Soy meal from extrusion methods typically
contains from about 5 to about 15 wt. % oil, preferably from about
8 to about 12 wt. % oil. The protein content of soy meal from
extrusion methods typically contains from about 35 to about 55 wt.
% protein, preferably from about 40 to about 48 wt. % protein.
[0078] Another method for producing soy meal is the
expansion/expelling method. This method has gained in popularity
over other methods because of the quality of the byproducts
produced, as well as elimination of environmental hazards
associated with solvent extraction methods. In the
expansion/expelling method, the raw soybeans are fed through a
series of augers, screeners, and controlled rate feeders into the
expanders. The internal expander chambers and grinders create
extreme temperature and pressure conditions, typically from about
150.degree. C. to about 177.degree. C. and from about 375 to about
425 psi. The oil cells of the bean are ruptured as the product, in
slurry form, exits the expander and the pressure drops down to
atmospheric pressure. The high frictional temperature cooks the
meal and oil, yielding a high quality product. About half of the 12
wt. % moisture present in the raw soybean is released as steam as
the slurry exits the expander. The water and steam mix inside the
expander, keeping the slurry fluid as well as aiding in the cooking
process. The hot soy meal slurry is then fed to a continuous oil
expeller. The meal is squeezed under pressure and the free oil is
expelled. The oil and the meal are then separated and recovered.
The soy meal exits the press as a mixture of dry powder and chunks,
which can be milled with a hammer mill, roller mill, or other
suitable mill to an acceptable bulk density and consistency. The
product can then be passed through a cooler where heat is
extracted. The resulting expanded/expelled soymeal typically
contains from about 7 to about 11 wt. % oil and from about 42 to
about 46 wt. % protein, on a dry matter basis.
[0079] To produce a soy meal suitable for use in the adhesives of
the preferred embodiments, it is preferably ground into fine flour.
Typically, the dry extracted meal is ground so that nearly all of
the flour passes through an 80 to 100 mesh screen. In certain
embodiments, flour milled to pass through higher or lower mesh
screen can be preferred, for example, about 20 mesh or less down to
about 150 mesh or more, more preferably from about 25, 30, 35, 40,
45, 50, 55, 60, 65, 70, or 75 mesh to about 80, 85, 90, 95, 100,
110, 120, 130, or 140 mesh. In the preferred embodiments, the soy
meal contains about 40 wt. % or more protein. However, soy meals
with lower protein content can also be suitable in certain
embodiments. Soy meals having various oil contents can be employed
in the preferred embodiments.
[0080] Denaturization and Stabilization of the Protein
[0081] The soy protein in soybeans is primarily a globular protein
consisting of a polypeptide chain made up of amino acids as
monomeric units. Proteins typically contain 50 to 2000 amino acid
residues per polypeptide chain. The amino acids are joined by
peptide bonds between the alpha-carboxyl groups and the alpha-amino
groups of adjacent amino acids, with the alpha-amino group of the
first amino acid residue of the polypeptide chain being free. The
molecular structures of soy proteins contain a hydrophilic region
that is enclosed within a hydrophobic region, such that many of the
polar groups are unavailable. It is the same forces that maintain
the helical structure of the protein that are desirable for
bonding. The globular shape of proteins in aqueous solution is a
consequence of the fact that the proteins expose as small a surface
as possible to the aqueous solvent so as to minimize unfavorable
polar interactions with the water and to maximize favorable
interactions of the amino acid residues with each other. The
conformation of the protein is maintained by disulfide bonds and by
non-covalent forces, such as van der Waals interactions, hydrogen
bonds, and electrostatic interactions.
[0082] When a protein is treated with a denaturant, the
conformation is lost because the denaturant interferes with the
forces maintaining the configuration. The result is that more polar
groups of the protein are available for reaction. In preparing the
adhesives of the preferred embodiments, the soy protein is first
denatured. The polar groups are uncoiled and exposed to facilitate
the development of a good adhesive bond.
[0083] The denaturant can include any material capable of
disrupting the intermolecular forces within the protein structure
by breaking hydrogen bonds and/or cleaving disulfide bonds.
Reagents that can be employed to cleave disulfide bonds include
oxidizing agents, such as formaldehyde and sodium bisulfite, and
other substances as are known in the art. Suitable denaturants
include, but are not limited to, organic solvents, detergents,
acids, bases, or even heat. Particularly preferred denaturants
include sodium hydroxide, potassium hydroxide, other alkali and
alkaline metal hydroxides, concentrated urea solutions, and mineral
acids. In the preferred embodiments, the alkali or acid treatments
are conducted at elevated temperatures. Preferably, metal
hydroxides, such as sodium hydroxide, are employed due to their
ability to elevate the pH to the desired level. A suitable pH
contributes to proper solubility of the soy flour or other protein,
as well as to catalysis of the copolymerization reaction with
comonomers, such as phenol formaldehyde. The amount of denaturant
employed is preferably the minimum amount that yields proper
methylolation. Excess denaturant is generally not preferred,
although in certain embodiments it can be acceptable or even
desirable to employ excess denaturant. Most preferably, the
denaturant is sodium hydroxide, which is preferably employed at an
amount of from about 5 wt. % or less to about 40 wt. % or more,
based on sodium hydroxide to protein, preferably from about 6, 7,
8, or 9 wt. % to about 30 or 35 wt. %, and most preferably from
about 10, 11, 12, 13, 14, or 15 wt. % to about 16, 17, 18, 19, 20,
21, 22, 23, 24, or 25 wt. %. The amount of sodium hydroxide
employed is preferably kept as low as possible, and the amount
employed is preferably directly related to the amount of protein
present in the flour. For a typical soy flour containing from about
40 to about 50 wt. % protein, the amount of sodium hydroxide is
preferably from about 8 to about 12 wt. %. If the amount of sodium
hydroxide is insufficient, inadequate methylolation can result,
which in turn can result in premature gelation upon formaldehyde
addition.
[0084] To aid in the solubility and compatibility of the soy flour,
compatibilizing materials can be employed. These include, but are
not limited to, ethylene glycol, poly(ethylene glycol), and other
ionic and non-ionic surfactants as are known in the art.
[0085] In preferred embodiments, a phase transfer catalyst is added
to the denaturing reaction mixture. The phase transfer catalyst
serves to enhance the rate of reaction occurring in a two phase
organic-aqueous system by catalyzing the transfer of water soluble
reactants across the interface to the organic phase. Suitable phase
transfer catalysts include polyethylene glycol, quaternary ammonium
compounds, and the like. In a preferred embodiment, the phase
transfer catalyst is tris(dioxa-3,6-heptyl)amine, commonly referred
to as Thanamine or TDA-1 (available from Rhodia, Inc. of Cranbury,
N.J.). In various embodiments, it is preferred to add a component
to the reaction mixture that enhances the solubility of the
protein, thereby facilitating the denaturing reaction. Certain
antioxidants, including tertiary-butylhydroquinone (TBHQ) and
butylated hydroxyanisole (BHA), are observed to increase the
solubility of soy protein, however, other suitable solubility
enhancers may also be used.
[0086] Denaturization can occur over a wide temperature range. The
denaturization reaction can be carried out at temperatures from
about 60.degree. C. or lower to about 140.degree. C. or higher,
preferably from about 65 to 70.degree. C. to about 100, 105, or
110.degree. C., and most preferably from about 75, 80, or
85.degree. C. to about 90 or 95.degree. C.
[0087] The denaturization time is dependent on the amount of
denaturant employed, the particle size of the flour or other
protein source, and the reaction temperature. Preferably, the
denaturization time is from about 1 minute or less to about 100
hours or more, preferably from about 2, 3, 4, or 5 minutes to about
3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 18, 24, 30, 36, 42, 48, 54, 60,
66, or 72 hours, and most preferably from about 10, 15, 20, 25, or
30 minutes to about 40, 50, 60, 70 80, 90, 100, 110, or 120
minutes. Excessive temperatures, reaction times, and/or denaturant
levels can lead to unacceptably high levels of hydrolysis, which in
turn results in high extractables and poor water resistance of the
cured adhesive. However, in certain embodiments, temperatures,
reaction times, and/or denaturant levels outside of the preferred
ranges can be tolerated, or even desired. Maintaining the proper
balance of denaturant, temperature, and time of reaction yields a
satisfactory denatured soy protein which can be employed in the
preparation of durable copolymer adhesives.
[0088] Soy flour tends to foam during heating in water.
Accordingly, it can be desirable to employ a suitable antifoam
agent. It is preferred that the level of antifoam does not exceed
2% of the total soy. Preferably, from about 0.01 g or less to about
0.2 g or more of antifoam agent is employed per 150 g flour, more
preferably from about 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, or 0.08 g
to about 0.09, 0.10, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, 0.17,
0.18, or 0.19 g antifoam agent per 150 g flour. Suitable antifoams
include siloxanes, fatty acids, fatty acid salts, and other
materials capable of reducing the surface tension of the soy flour
in solution.
[0089] Formaldehyde can also be employed to improve the solubility
and stability of the protein in the dissolved state.
[0090] The Soy Methylolation Reaction
[0091] The adhesives of the preferred embodiments are based on a
solubilized protein. The solubilized protein is reacted with
formaldehyde to form methylol derivatives. Methylolated proteins
react with the comonomer to form thermoset adhesives.
[0092] After denaturing the soy flour, the next step in the
preparation of the adhesives of the preferred embodiment is the
stabilization of the denatured protein. This is accomplished by
reacting the denatured protein with an aldehyde, for example,
formaldehyde, a formaldehyde generator, acetaldehyde,
propionaldehyde, glyoxal, or mixtures thereof. The preferred
embodiment employs formaldehyde or a formaldehyde generator to
methylolate the protein. The methylolation (also referred to as
hydroxymethylation) of the denatured protein's polypeptide chain
yields a stabilized protein.
[0093] If the denatured soy protein is not subject to methylolation
prior to condensation with suitable copolymers, the resin system
can be very reactive at room temperature and offer poor viscosity
stability, such as the two part adhesive systems employed in the
"honeymoon" finger jointing process developed by Dr. Roland
Kreibich. This reactivity is managed in order to provide a stable
one-component resin system. Thus, the methylolation reaction is
carried out prior to copolymerization by adding formaldehyde, or a
latent source of formaldehyde, to the denatured soy protein.
[0094] The formaldehyde (or formaldehyde source) is added in an
amount of from about 10 wt % or less to about 60 wt. % or more to
the soy flour, preferably from about 11, 12, 13, 14, or 15 wt. % to
about 35 or 40 wt. %, and most preferably from about 20, 21, 22,
23, 24, or 25 wt. % to about 26, 27, 28, 29, or 30 wt. %. The
methylolation reaction can be carried out under a variety of
conditions, including various concentrations, temperatures, and
reaction times. For stabilized proteins, concentrations of from
about 20, 15, or 10 wt. % or less to about 50, 55, or 60 wt. % or
more solids are acceptable, preferably about 21, 22, 23, 24, or 25
wt. % to about 26, 27, 28, 29, 30, 31, 32, 33, 34, or 35 wt. % are
employed.
[0095] Suitable methylolation temperatures are from about 0.degree.
C. or less to about 140.degree. C. or more, preferably from about
5, 10, 15, 20, 25, or 30.degree. C. to about 95, 100, 105, or
110.degree. C., and most preferably from about 30, 35, 40, 45 or
50.degree. C. to about 55, 60, 65, 70, 75, 80, 85, or 90.degree. C.
The methylolation reaction occurs via reaction of the electrophilic
aldehyde with a terminal amine of the protein or via reaction with
the protein's amino acid nucleophilic side chains. Preferably,
formaldehyde or latent sources of formaldehyde are employed;
however, any electrophilic aldehyde capable of reacting with the
nucleophilic components of the denatured soy flour can be
employed.
[0096] Generally, over 28% of the total amino acid composition in
soy protein contains nucleophilic side groups that are capable of
reacting with formaldehyde to form a reactive soy methylol group
that can be further copolymerized with suitable copolymers.
Additionally, the electrophilic side group of tyrosine is also
capable of reacting with formaldehyde to generate a reactive soy
methylol group that can be further copolymerized with suitable
copolymers. The amine nitrogens within the protein chains and the
end group amines are also capable of reacting with formaldehyde to
form reactive methylol intermediates. The denatured soy flour is
methylolated to provide an adhesive with the reactivity,
durability, and room temperature stability desired for a practical
one-component soy based adhesive. For illustrative purposes, a
typical end group and side chain methylolation reactions are shown
below. 1
[0097] Comonomer Reactions
[0098] The chemistries of the comonomer reactions are similar to
those involved in curing the adhesives. Comonomers can be formed in
situ with the stabilized protein, or can be formed separately and
mixed with the stabilized protein in the methylolation or
oligomerization reaction step. Suitable chemistries include phenol,
melamine, urea, and combinations thereof reacting with formaldehyde
or a formaldehyde generator. The process for making such resins is
a two step process involving methylolation followed by
condensation. These same two steps can be employed in conjunction
with the soy flour based resin systems of preferred embodiments,
along with an additional denaturization step prior to
methylolation.
[0099] Methylolation Reaction
[0100] The methylolation reaction for many adhesive systems
involves the reaction of a nucleophilic material with an
electrophilic aldehyde. Typically, formaldehyde or latent sources
of formaldehyde, such as paraformaldehyde, are employed. With
phenol, the methylolation reaction involves the substitution of the
phenol's ortho hydrogen(s) and/or the para hydrogen with
hydroxymethyl groups. This reaction yields a mixture of mono-, di-
and tri-substituted methylolated products. The reactivity of the
para position is approximately 1.4 times greater than that of the
ortho positions. However, since each phenol has two ortho positions
but only one para position, substitution is seen more often at the
ortho position. Similar reactions occur with other common
nucleophilic starting materials, such as urea and melamine. These
processes are often base-catalyzed to enhance the nucleophilicity
of the starting material. For phenol, as the extent of
methylolation increases, the pKa of the intermediate products
decreases, which can result in large amounts of undesired,
unreacted phenol in the final product. Several base catalyzed
methylolation reactions are shown below. 2
[0101] The methylolation process typically does not result in a
substantial molecular weight increase in the resin. This step is
more properly considered a process of adding functionality to the
starting reactants to prepare them for the condensation step,
wherein molecular weight increases and matrix development
occurs.
[0102] Condensation
[0103] The condensation step is a process of increasing the
molecular weight of the resin though a series of Mannich-type
reactions involving the methylolated precursors. These reactions
proceed in the same manner as other condensation or step-growth
polymerizations. That is, the molecular weight is increased until
gelation occurs. The condensation of any of the methylolated
materials described above is readily carried out by either a
chemically or thermally driven process. With urea, the condensation
occurs under acidic conditions. For phenolic resins, the
condensation can be accomplished under either acid or basic
conditions.
[0104] It is generally preferred that high methylol containing
materials (resoles) undergo the condensation reaction at a pH of
from about 9 or less to about 12 or more. Low to no methylol
containing phenolics (novolaks) undergo the condensation reaction
under acidic conditions in the presence of additional latent
sources of formaldehyde. For phenolic systems, the condensation
reaction is much faster than the methylolation reaction under
acidic conditions, whereas the opposite is true under alkaline
conditions. While not wishing to be bound to any particular theory,
it is generally believed that the condensation mechanism involves
the condensation of two methylol groups to yield one molecule of
water and an ether linkage. This ether linkage is considered to be
very unstable and collapses quickly into a more stable methylene
linkage liberating an additional molecule of formaldehyde that can
further methylolate. Condensation can also take place between a
methylol group and a reactive non-substituted ortho or para site on
the phenolic ring or between two methylol groups. Examples of the
condensation process are described below. 3
[0105] Copolymerization and Condensation of the Stabilized Protein
and Comonomer
[0106] After methylolation of the denatured soy protein and, in
certain embodiments, the comonomer, the next step in the
preparation of the adhesives of the preferred embodiments involves
condensation (also referred to as "resinification" or "curing") of
the methylolated, denatured soy flour with itself and with suitable
comonomers. Although the methylolated soy flour can be
self-condensed to a certain degree, many of these bonds are often
considered to be readily reversible and hydrolyzable, thus a
suitable reactive comonomer is employed to increase the hydrolytic
stability and thus increase the durability of the adhesive and the
adhesive bond.
[0107] The copolymerization condensation can occur in various
fashions. One of the reactions that can occur is the condensation
of a protein hydroxymethyl group with either a hydroxy methylol
group of phenol or a reactive ortho or para hydrogen of phenol.
Both mechanisms result in the formation of the stable
N--CH.sub.2-phenol linkage. 4
[0108] Copolymerization is also possible between two protein
hydroxymethyl groups, yielding a protein-CH.sub.2-protein methylene
linkage. Any comonomer capable of reacting with the methylol
protein that affords a durable non-hydrolyzable stable bond is
suitable. Examples of suitable comonomers include, but are not
limited to, phenol, urea, melamine urea, melamine, and any
methylolated derivatives thereof. Additionally, isocyanates, such
as polymeric methylenediphenyl diisocyanate, are also suitable
comonomers.
[0109] The comonomers employed can have a variety of methylol
functionalities and molecular weights. For phenol, the methylol
functionality is from about 0 to about 3 moles or more methylol to
phenol, preferably from about 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7,
0.8, 0.9, 1.0, 1.2, 1.3, or 1.4 to about 2.6, 2.7, 2.8, or 2.9
moles, and most preferably from about 1.5, 1.6, 1.7, 1.9 or 1.9 to
about 2.0, 2.1, 2.2, 2.3, 2.4, or 2.5 moles. The condensation
reaction can be affected by the amount of acid or base present in
the system. For phenol, it is preferred that the sodium hydroxide
level in the copolymer be from about 0.01 moles or less to about
1.0 moles or more of sodium hydroxide phenol, preferably from about
0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.10, 0.11, 0.12,
0.13, 0.14, 0.15, 0.16, 0.17, 0.18, or 0.19 moles to about 0.55,
0.60, 0.65, 0.70, 0.75, 0.80, 0.85, 0.90, or 0.95 moles, most
preferably from about 0.20, 0.21, 0.22, 0.23, 0.24, 0.25, 0.26,
0.27, 0.28, 0.29, or 0.30 moles to about 0.31, 0.32, 0.33, 0.34,
0.35, 0.36, 0.37, 0.38, 0.39, 0.40, 0.41, 0.42, 0.43, 0.44, 0.45,
0.46, 0.47, 0.48, 0.49, or 0.50 moles. Higher or lower alkalinities
can be employed, depending upon the amount of denaturant used.
[0110] The pH of the final adhesive resin for optimal durability is
generally from about 9 or less to about 12 or more, preferably from
9.1, 9.2, 9.3, 9.4, 9.5, 9.6, 9.7, 9.8, or 9.9 to about 11.6, 11.7,
11.8, or 11.9, most preferably from about 10, 10.1, 10.2, 10.3,
10.4, 10.5, 10.6, 10.7, 10.8, or 10.9 to about 11, 11.1, 11.2,
11.3, 11.4, or 11.5. If the pH of the adhesive is less than 9,
additional base, such as sodium hydroxide, can be added to decrease
the viscosity of the adhesive. If the final adhesive has a pH over
12, the resin may not properly cure, leading to poor performing
resins. In certain embodiments, a pH of less than 9 or greater than
12 can be tolerated, or is even desirable. After the adhesive is
formulated into the acid dispersion, then a pH of less than about 6
is preferred for the dispersion.
[0111] The introduction of the comonomer to the methylolated,
denatured soy flour can be accomplished by either blending the two
reactive components or by generating the reactive comonomer in-situ
with the methylolated, denatured soy flour. This permits the final
adhesive to be prepared from either a blend or in a one-pot
process. Regardless of the mode of introduction of the comonomer,
it is desirable to introduce small amounts of commoner into the
methylolated, denatured soy flour prior to final addition of the
total comonomer. This permits small amounts of low molecular weight
copolymer to be formed and also functionalizes the methylolated,
denatured soy flour such that it is more reactive toward additional
comonomer added later through blending or prepared in situ in a
one-pot process. Comonomer can be added before or after the acidic
adhesive dispersion is formed. Preferably, the addition of
comonomer, such as polymeric methyl diphenyl diisocyanate (PMDI) or
novolak resin, occurs after the dispersion is formed.
[0112] The amount of comonomer added to the adhesive can be from 20
wt. % or less to 99 wt. % or more. For applications where
durability is of less importance, an amount of from about 21, 22,
23, 24, 25, 26, 27, 28, or 29 wt. % to about 41, 42, 43, 44, 45,
46, 47, 48, 49, or 50 can be employed, preferably from about 30,
31, 32, 33, 34, or 35 to about 36, 37, 38, 39, or 40 wt. %. For
applications where high durability is desired, from about 50, 51,
52, 53, 54, 55, 56, 57, 58, or 59 wt. % to about 71, 72, 73, 74,
75, 76, 77, 78, 79, or 80 wt. % can be employed, preferably from
about 60, 61, 62, 63, 64, or 65 wt. % to about 66, 67, 68, 69, or
70 wt. %. A mixture of comonomers can also be employed.
[0113] The rate of copolymerization can be increased by the
addition of cure accelerators or catalysts. Typical cure
accelerators include propylene carbonate, ethyl formate, and other
alpha esters. Catalysts, such as sodium or potassium carbonate, can
also be added to increase the rate of reaction and also the resin
solids content.
[0114] In a particularly preferred embodiment, in addition to a
comonomer, the methylolated protein is reacted with a coreacting
prepolymer of the comonomer that optionally has one or more
methylol groups. The molecular weight of the prepolymer is selected
based on the desired level of penetration and the total soy amount.
The molecular weight of the prepolymer can also affect cure speed.
The prepolymer preferably comprises up to about 30 or more
repeating units, more preferably from 2, 3, or 4 repeating units up
to 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21,
22, 23, 24, 25, 26, 27, 28, or 29 repeating units. Particularly
preferred prepolymers include phenol formaldehyde, however any
prepolymer capable of reacting with the methylolated protein can be
employed. Typically, from about 0 to about 60 wt. % of the adhesive
is contributed by the prepolymer Preferably, from about 5, 10, 15,
20, 25, or 30 wt. % up to about 35, 40, 45, 50, or 55 wt. % of the
adhesive is contributed by the prepolymer.
[0115] Preparation of Adhesives by Alternative Method
[0116] In certain embodiments, it can be desired to prepare an
adhesive by a simplified method involving fewer steps. Such a
method is described in copending U.S. application Ser. No.
10/211,944 filed Aug. 1, 2002, and entitled "VEGETABLE PROTEIN
ADHESIVE COMPOSITIONS." In the simplified method, the soy protein
and one or more co-monomers are polymerized. In order for the
polymerization reaction to occur, the soy protein is first
subjected to methylolation. If the co-monomers do not already
contain methylol groups, they too are subjected to methylolation
prior to the polymerization reaction. Preferred co-monomers include
any molecule containing methylol groups, or any molecule which may
undergo methylolation, for example, via reaction with formaldehyde.
Non-limiting examples of suitable methylol-containing molecules
include dimethylol urea, trimethylol melamine, tetramethylol ketone
and dimethylol phenol. Nonlimiting examples of suitable co-monomers
capable of undergoing methylolation via reaction with formaldehyde
include urea, melamine, and phenol. In preferred embodiments, the
co-monomer is capable of substitution by two, three, four or more
methylol groups. Generally, co-monomers having more methylol
substituents are more reactive than co-monomers having fewer
methylol substituents.
[0117] A single co-monomer or mixtures of two or more co-monomers
may be used in the adhesives prepared according to the simplified
method. A preferred co-monomer mixture contains methylol ketone and
methylol phenol. Different co-monomers possess different properties
and characteristics. By combining two or more co-monomers having
different characteristics, an adhesive having properties that
render it especially suitable for a particular application may be
obtained.
[0118] The first step in the preparation of the adhesives by the
simplified method involves methylolation of the denatured protein's
polypeptide chain, along with methylolation of any of the
co-monomers that do not already incorporate methylol groups. Any
suitable reaction may be used to functionalize the protein or
co-monomer with hydroxymethyl groups. In preferred embodiments,
however, the methylolation reaction proceeds by reacting the
protein or co-monomer with formaldehyde in the presence of an acid
or base catalyst. The methylolation of the protein and the
co-monomer(s) may be conducted simultaneously in the same reaction
mixture, or may be conducted separately for each component.
Methylolation of proteins and amines such as urea and melamine
typically involves substitution of primary and/or secondary aminic
hydrogens by hydroxymethyl groups. When the co-monomer is phenol,
the methylolation reaction involves replacing the phenol molecule's
two ortho hydrogens or an ortho hydrogen and a para hydrogen with
hydroxymethyl groups. The reaction yields a mixture of
2,4-dimethylol phenol and 2,6-dimethylol phenol. When the
co-monomer is acetone, a methyl hydrogen is replaced by a
hydroxymethyl group. Typical methylolation reactions for a
polypeptide and selected co-monomers are illustrated below. 5
[0119] The methylolated co-monomers are commercially available and
may be purchased from selected resin manufacturers. Alternatively,
co-monomers that are not methylolated or are only partially
methylolated may be subjected to a methylolation step as part of
the process of preparing the adhesives of preferred embodiments.
When methylolating the co-monomer starting material, it is
preferred to conduct the methylolation at a pH of about 8.4 to
about 10.5, however, in certain embodiments a higher or lower pH
may be suitable. The methylolation reaction is preferably conducted
at a temperature of about 32.degree. C. to about 75.degree. C.
Higher or lower temperatures may also be suitable, depending upon
the reactivity of the compound to be methylolated or other factors.
Reaction times of from about 20 minutes to two hours are typically
sufficient to ensure complete methylolation. However, as will be
appreciated by one skilled in the art, the methylolation reaction
may proceed more rapidly or more slowly in certain embodiments,
resulting in a shorter or longer reaction time.
[0120] Methylolation of the polypeptide chains of the soy protein
and the non-methylolated or partially-methylolated co-monomer may
preferably be conducted at the same time in the same reaction
mixture, so as to provide an even simpler process. However, the
methylolation of the polypeptide chains of the soy protein may be
conducted separately from that of the non-methylolated or
partially-methylolated co-monomer in certain embodiments.
[0121] After methylolation of the soy protein and, in certain
embodiments, the co-monomer, the next step in the preparation of
the adhesives by the simplified method involves polymerization
(also referred to as resinification or curing) of the protein and
co-monomer molecules. One of the reactions in the polymerization
process involves the condensation of a methylol group with an amine
group to liberate water and form a methylene bridge. Another
reaction in this process involves condensation of two methylol
groups to yield an unstable ether linkage, which undergoes a
reaction to liberate formaldehyde, thereby forming a methylene
bridge. This free formaldehyde then reacts with the reactive amine
groups of the polypeptide to form additional methylol groups.
Methylol groups are also capable of condensing with
non-methylolated hydroxyl groups to form unstable ether
linkages.
[0122] Because each protein molecule typically contains methylol
groups and groups that are reactive to methylol groups, significant
crosslinking occurs. In preferred embodiments, the reaction is
conducted at elevated temperature. Preferred temperatures are
typically between 65.degree. C. and 110.degree. C. However, higher
or lower temperatures may be preferred in certain embodiments, as
will be appreciated by one skilled in the art. Typical condensation
reactions between a methylolated protein and either a
2,6-methylolated urea or 2,6-dimethylol phenol are depicted below.
6
[0123] As stated above, the ether linkages formed in certain of the
condensation reactions are not stable. At elevated temperatures or
under acidic conditions, formaldehyde is spontaneously liberated
from the linked molecules to yield a methylene bridge. The released
formaldehyde may then participate in further methylolation
reactions. The formation of the methylene bridge in a methylolated
protein molecule coupled to either methylolated urea or
methylolated phenol is depicted below. 7
[0124] Additives
[0125] Many additives can be employed in the preparation of
adhesive resins. These additives can lower viscosity, increase cure
speed, assist resin flow and distribution, extend shelf life, or
lower the cost of the resin. Such additives include, but are not
limited to, urea, sodium carbonate, and sodium bicarbonate. Any
suitable additive can be employed, provided that the water
resistance of the resin is acceptable. A water extraction of the
resin of less than about 35% is generally preferred. However, in
certain embodiments a higher water extraction can be acceptable.
Due to the foaming nature of soy flour upon heating in a water
solution, an antifoam agent can be advantageously employed,
preferably at a concentration of less than 2% of the total soy
flour in the formula. It is generally preferred to employ as little
antifoam agent as possible.
[0126] Preparation of Adhesive Dispersions
[0127] In certain applications, it is desirable to employ the
adhesives of preferred embodiments in the form of a dispersion in
acidic solution. Any suitable acid can be employed in preparing the
solution. Suitable acids include, but are not limited to, sulfuric
acid, hydrochloric acid, formic acid, acetic acid, nitric acid, and
phosphoric acid. Sulfuric acid is particularly preferred. It is
generally preferred that the acid is an aqueous solution. However,
any suitable solvent can be employed. Suitable solvents include
water, ethanol, methanol, acetonitrile, acetone, pyridine,
tetrahydrofuran, and other compatible solvents. In certain
embodiments, the acid can be added to the adhesive in undiluted
form. For example, undiluted acetic acid or sulfuric acid can be
employed.
[0128] It is generally preferred to prepare the dispersion by
adding the acid to the adhesive at a temperature of from about
0.degree. C. or lower to about 90.degree. C. or higher. Optionally
warming the resin to a temperature of 10.degree. C. or higher can
facilitate formation of the dispersion. A resin temperature of from
about 11, 12, 13, or 14.degree. C. to about 35, 40, 45, or 50, 55,
60, 65, 70, 75, 80, 85, or 90.degree. C. is generally preferred,
with a temperature of from about 15, 16, 17, 18, or 19, or
20.degree. C. to about 21, 22, 23, 24, 25, 26, 27, 28, 29 or
30.degree. C. is more preferred. Lower temperatures are generally
preferred so as for avoid the formation of excessive particulate
matter, which tends to occur at higher temperatures. While it is
generally preferred to avoid formation of excessive particulate
matter, in certain embodiments the formation of such particulate
matter can be acceptable, or even desirable. While it is generally
preferred to warm the resin, in certain embodiments it can be
desirable to cool the resin to facilitate formation of a dispersion
with desired properties.
[0129] Sufficient acid is added to the adhesive such that the pH is
decreased to near neutral (6.0) or lower, preferably from about 1
or lower to about 6, more preferably from about 1.5, 2, 2.5, 3, or
3.5 to about 5.5, and most preferably from about 4 or 4.5 to about
5. The amount of acid employed depends upon the starting pH and the
desired resulting pH. For example, when sulfuric acid is employed
with the resins of the preferred embodiments, from about 1 part or
less to about 10 parts or more concentrated sulfuric acid is
employed per 100 parts adhesive, preferably from about 1, 1.5, 2,
2.5, or 3 parts to about 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9,
or 9.5 parts sulfuric acid, and most preferably about 3.5 parts
sulfuric acid.
[0130] Preparation of acidic dispersions of the adhesives of
preferred embodiments can offer several advantages. These
advantages include additional copolymerization taking place in the
acidic dispersion, greater soy reactivity during copolymerization
as demonstrated by lower extractables, greater room temperature
stability, lower viscosity, and the ability to employ higher soy
levels (up to 75 wt. % or more, for example, on a total soy plus
phenol basis). The acidic conditions in the dispersion also permit
a greater selection of crosslinking agents to be employed, for
example, urea formaldehyde, melamine formaldehyde, novolak phenol
formaldehyde, and isocyanates (such as polymeric methylene
dipara-phenylene isocyanate).
[0131] Use of Adhesives in Composition Boards
[0132] The adhesives of preferred embodiments are suitable for use
in a variety of applications, including, but not limited to,
applications in which conventional resin adhesives are typically
used. One particularly preferred application for the adhesives of
the preferred embodiments is in the manufacture of composition
boards. Oriented strand boards (face and core sections), plywood,
particleboard, laminated veneer lumber, and fiberboards are a few
examples of possible applications of the resin systems of preferred
embodiments. Composition boards can be fabricated from any suitable
wood or agricultural material, such as wood, straw (wheat, rice,
oat, barley, rye, flax, grass), stalks (corn, sorghum, cotton),
sugar cane, bagasse, reeds, bamboo, cotton staple, core (jute,
kenaf, hemp), papyrus, bast (jute, kenaf, hemp), cotton linters,
esparto grass, leaf (sisal, abaca, henequen), sabai grass, small
diameter trees, stand improvement tree species, mixed tree species,
plantation residues and thinnings, point source agricultural
residues, and recycling products such as paper and paper-based
products and waste, and the like. Composition boards prepared using
the adhesives of the preferred embodiments possess acceptable
physical properties as set forth in industry standards and offer
the possibility of lower cost and/or lower volatility products. The
resins, such as the soy-based resins, of the preferred embodiments
can be applied using conventional equipment such as spinning disk
atomizers, spray atomizers, and the like.
[0133] Phenol is regulated under the Resource Conservation and
Recovery Act, and is listed by the U.S. Environmental Protection
Agency (EPA) as a water priority pollutant, a volatile organic
compound, and an air toxic listed on the hazardous air pollutant
list. Very high concentrations of phenol can cause death if
ingested, inhaled or absorbed through skin, and exposure to lower
concentrations can result in a variety of harmful health effects.
Formaldehyde exposure is also regulated by various governmental
agencies, including the U.S. Occupational Safety and Health
Administration. If formaldehyde is present in the air at levels at
or above 0.1 ppm, acute health effects can occur. Sensitive people
can experience symptoms at levels below 0.1 ppm, and persons have
been known to develop allergic reactions to formaldehyde through
skin contact. Formaldehyde has caused cancer in laboratory animals
and may cause cancer in humans.
[0134] Because of the adverse health effects associated with
exposure to phenol and formaldehyde, adhesives prepared using
phenol and formaldehyde as starting materials that have a low level
of free phenol and free formaldehyde in the finished adhesive are
desirable. Especially desirable are adhesives that comply with EPA
regulations for low Volatile Organic Compound (VOC) products.
Preferably, the adhesives of preferred embodiments contain less
than about 2.5 wt. % free phenol. More preferably, the adhesives
contain less than about 2.25, 2, 1.75, 1.5, 1.25, 1, 0.75, 0.5,
0.25, 0.1, 0.05, 0.01, 0.005 or 0.001 wt. % free phenol.
Preferably, the adhesives of preferred embodiments contain less
than about 1% free formaldehyde. More preferably, the adhesives
contain less than about 0.75, 0.5, 0.25, 0.1, 0.075, 0.05, 0.025,
0.01, 0.0075, 0.005, 0.0025, or 0.001 wt. % free formaldehyde.
[0135] The physical properties of composition boards are measured
according to standards set forth by ASTM International in
"Standards and Methods of Evaluating the Properties of Wood-Base
Fiber and Particle Panel Materials." Tensile strength perpendicular
to the surface, also referred to as internal bond, provides a
measure of how well the board is glued together. The value is
reported in psi or Pa. The acceptable range for interior
applications varies depending upon the grade of composition board.
This test is currently not used extensively, but may become more
widely used as the composition board industry moves towards greater
production of boards for use in structural applications.
[0136] Water resistance is evaluated by submerging a sample of
board in water at room temperature for 24 hours and by submerging
another sample in boiling water for 2 hours. Typically, only the 24
hour test is conducted, unless the panel is used in structural or
construction applications. In the water resistance test, the
thickness of the board is measured before and after submerging the
sample in water. The thickness swell is then measured as the
percent increase in thickness relative to the dry thickness.
EXAMPLES
Comparative Example 1
[0137] A resin was prepared by combining components in the order as
listed in Table 1.
1TABLE 1 Stage I Sequence Ingredient Amount (g) % to Soy 01 Water
268.0 02 NaOH 100% 8.0 8.0 03 Poly(ethylene glycol) 3.0 3.0 04 Soy
Flour 100.0 Stage II Sequence Ingredient Amount (g) Moles to Phenol
05 Phenol 90% 47.0 1.0 06 Formaldehyde 37% 87.5 2.4 Total 513.5
[0138] In Stage 1, water, NaOH, and poly(ethylene glycol) were
combined while mixing. The mixture was heated to 80.degree. C. with
modest agitation. Soy flour was added at a rate of 5% of the total
soy flour per minute to the mixture with rapid stirring. The
mixture was heated to approximately 100.degree. C. over 15 minutes.
The maximum temperature reached was 97.degree. C. The temperature
was maintained at 96-98.degree. C. for 1 hour.
[0139] In Stage 2, the mixture was removed from the heat source and
charged with phenol and formaldehyde over 10 minutes, during which
the temperature fell to 90.degree. C. The mixture was then
subjected to a vacuum distillation for 80 minutes and then cooled
to 40.degree. C. in a cold water bath for 10-15 minutes. The
resulting solution was filtered through a coarse screen.
Example 2
[0140] A resin was prepared by combining components in the order as
listed in Table 2 to yield a 70/30 phenol formaldehyde soy resin
with 100 % low molecular weight phenol formaldehyde.
2TABLE 2 Stage I Sequence Ingredient Amount (g) % to Soy 01 Water
220.0 02 NaOH 100% 6.8 8.0 03 Ethylene Glycol 1.3 1.5 04 Soy Flour
85.0 Stage II Sequence Ingredient Amount (g) Moles to Phenol 05
Formaldehyde 37% 122.0 1.04 06 Phenol 100% 136.1 1.00 07 NaOH 100%
5.8 0.10 08 Formaldehyde 37% 122.0 1.04 09 NaOH 100% 2.9 0.05 10
NaOH 100% 2.9 0.05 Total 704.8
[0141] In Stage 1, water was combined with NaOH and ethylene glycol
with mixing. The mixture was heated to 70.degree. C. with modest
agitation. Soy flour was added to the mixture at 5% of the total
soy flour per minute with rapid stirring. The mixture was heated to
90.degree. C. over 15 minutes, and maintained at a temperature of
88-92.degree. C. for 1 hour.
[0142] In Stage 2, the mixture was removed from the heat source and
charged with formaldehyde over 10 minutes, then the solution was
maintained at 75.degree. C. for 20 minutes. Phenol was added to the
mixture over 10 minutes, and then NaOH was added. The solution was
heated to 75.degree. C., and formaldehyde was added over 10 minutes
while maintaining the temperature at 75.degree. C. NaOH was then
added, and the mixture held at 75.degree. C. for 5 minutes, then
the remaining NaOH was added. After maintaining the mixture at
75.degree. C. for an additional 90 minutes, it was cooled to
40.degree. C. in a cold water bath over 10-15 minutes. The solution
was filtered through a coarse screen.
Example 3
[0143] A resin was prepared by combining components in the order as
listed in Table 3 to yield a 60/40 phenol formaldehyde soy resin
with 100 % low molecular weight phenol formaldehyde.
3TABLE 3 Stage I Sequence Ingredient Amount (g) % to Soy 01 Water
270.2 02 NaOH 100% 10.0 8.0 03 Ethylene Glycol 1.9 1.5 04 Soy Flour
125.0 Stage II Sequence Ingredient Amount (g) Moles to Phenol 05
Formaldehyde 37% 115.4 1.04 06 Phenol 100% 128.6 1.00 07 NaOH 100%
5.5 0.10 08 Formaldehyde 37% 115.4 1.04 09 NaOH 100% 2.7 0.05 10
NaOH 100% 2.7 0.05 Total 777.4
[0144] In Stage 1, water was combined with NaOH and ethylene glycol
with mixing. The mixture was heated to 70.degree. C. with modest
agitation. Soy flour was added to the mixture at 5% of the total
soy flour per minute with rapid stirring. The mixture was heated to
90.degree. C. over 15 minutes, and maintained at a temperature of
88-92.degree. C. for 1 hour.
[0145] In Stage 2, the mixture was removed from the heat source and
charged with formaldehyde over 10 minutes, then the solution was
maintained at 75.degree. C. for 20 minutes. Phenol was added to the
mixture over 10 minutes, and then NaOH was added. The solution was
heated to 75.degree. C., and formaldehyde was added over 10 minutes
while maintaining the temperature at 75.degree. C. NaOH was then
added, and the mixture held at 75.degree. C. for 5 minutes, then
the remaining NaOH was added. After maintaining the mixture at
75.degree. C. for an additional 90 minutes, it was cooled to
40.degree. C. in a cold water bath over 10-15 minutes. The solution
was filtered through a coarse screen.
Example 4
[0146] A resin was prepared by combining components in the order as
listed in Table 4 to yield a 60/40 phenol formaldehyde soy isolate
resin with 100% low molecular weight phenol formaldehyde.
4TABLE 4 Stage I Sequence Ingredient Amount (g) % to Soy 01 Water
292.9 02 NaOH 100% 20.0 16.0 03 Ethylene Glycol 1.9 1.5 04 Soy
Isolates 125.0 Stage II Sequence Ingredient Amount (g) Moles to
Phenol 05 Formaldehyde 37% 124.6 1.04 06 Phenol 100% 139.0 1.00 07
NaOH 100% 5.9 0.10 08 Formaldehyde 37% 125.6 1.04 09 NaOH 100% 3.9
0.05 10 NaOH 100% 2.9 0.05 Total 839.8
[0147] In Stage 1, water was combined with NaOH and ethylene glycol
with mixing. The mixture was heated to 70.degree. C. with modest
agitation. Soy isolates were added to the mixture at 5% of the
total soy isolates per minute with rapid stirring. The mixture was
heated to 90.degree. C. over 15 minutes, and maintained at a
temperature of 88-92.degree. C. for 1 hour.
[0148] In Stage 2, the mixture was removed from the heat source and
charged with formaldehyde over 10 minutes, then the solution was
maintained at 75.degree. C. for 20 minutes. Phenol was added to the
mixture over 10 minutes, and then NaOH was added. The solution was
heated to 75.degree. C., and formaldehyde was added over 10 minutes
while maintaining the temperature at 75.degree. C. NaOH was then
added, and the mixture held at 75.degree. C. for 5 minutes, then
the remaining NaOH was added. After maintaining the mixture at
75.degree. C. for an additional 90 minutes, it was cooled to
40.degree. C. in a cold water bath over 10-15 minutes. The solution
was filtered through a coarse screen.
Example 5
[0149] A resin was prepared by combining components in the order as
listed in Table 5 to yield a 50/50 phenol formaldehyde soy resin
with 100% low molecular weight phenol formaldehyde.
5TABLE 5 Stage I Sequence Ingredient Amount (g) % to Soy 01 Water
571.5 02 NaOH 100% 24.0 8.0 03 Ethylene Glycol 4.5 1.5 04 Soy Flour
300 Stage II Sequence Ingredient Amount (g) Moles to Phenol 05
Formaldehyde 37% 184.6 1.04 06 Phenol 100% 205.8 1.00 07 NaOH 100%
8.8 0.10 08 Formaldehyde 37% 184.6 1.04 09 NaOH 100% 4.4 0.05 10
NaOH 100% 4.4 0.05 Total 1492.6
[0150] In Stage 1, water was combined with NaOH and ethylene glycol
with mixing. The mixture was heated to 70.degree. C. with modest
agitation. Soy flour was added to the mixture at 5% of the total
soy flour per minute with rapid stirring. The mixture was heated to
90.degree. C. over 15 minutes, and maintained at a temperature of
88-92.degree. C. for 1 hour.
[0151] In Stage 2, the mixture was removed from the heat source and
charged with formaldehyde over 10 minutes, then the solution was
maintained at 75.degree. C. for 20 minutes. Phenol was added to the
mixture over 10 minutes, and then NaOH was added. The solution was
heated to 75.degree. C., and formaldehyde was added over 10 minutes
while maintaining the temperature at 75.degree. C. NaOH was then
added, and the mixture held at 75.degree. C. for 5 minutes, then
the remaining NaOH was added. After maintaining the mixture at
75.degree. C. for an additional 90 minutes, it was cooled to
40.degree. C. in a cold water bath over 10-15 minutes. The solution
was filtered through a coarse screen.
Example 6
[0152] A resin was prepared by combining components in the order as
listed in Table 6 to yield a 66/34 phenol formaldehyde soy resin
with 100% low molecular weight phenol formaldehyde.
6TABLE 6 Stage I Sequence Ingredient Amount (g) % to Soy 01 Water
285.9 02 NaOH 100% 12.0 8.0 03 Ethylene Glycol 2.25 1.5 04 Soy
Flour 150 Stage II Sequence Ingredient Amount (g) Moles to Phenol
05 Formaldehyde 37% 48.9 1.29 06 Phenol 100% 44.1 1.00 07 NaOH 100%
3.75 0.20 08 Formaldehyde 37% 80.4 2.11 09 NaOH 100% 1.9 0.10 10
NaOH 100% 1.9 0.10 Total 631.1
[0153] In Stage 1, water was combined with NaOH and ethylene glycol
with mixing. The mixture was heated to 70.degree. C. with modest
agitation. Soy flour was added to the mixture at 5% of the total
soy flour per minute with rapid stirring. The mixture was heated to
90.degree. C. over 15 minutes, and maintained at a temperature of
88-92.degree. C. for 1 hour.
[0154] In Stage 2, the mixture was removed from the heat source and
charged with formaldehyde over 5 minutes, while maintaining at a
temperature of 90.degree. C. for an additional 55 minutes after the
addition was complete. Phenol was added to the mixture over 10
minutes and the solution was cooled to 75.degree. C., then NaOH was
added. Formaldehyde was added over 10 minutes while maintaining the
temperature at 75.degree. C. NaOH was then added, and the mixture
held at 75.degree. C. for 5 minutes, then the remaining NaOH was
added. After maintaining the mixture at 75.degree. C. for an
additional 90 minutes, it was cooled to 40.degree. C. in a cold
water bath over 10-15 minutes. The solution was filtered through a
coarse screen.
Example 7
[0155] A resin was prepared by combining components in the order as
listed in Table 7 to yield a 30/70 phenol formaldehyde soy resin
with 100% low molecular weight phenol formaldehyde.
7TABLE 7 Stage I Sequence Ingredient Amount (g) % to Soy 01 Water
760.1 02 NaOH 100% 32.0 8.0 03 Ethylene Glycol 6.0 1.5 04 Soy Flour
400 Stage II Sequence Ingredient Amount (g) Moles to Phenol 05
Formaldehyde 37% 105.5 1.04 06 Phenol 100% 117.6 1.00 07 NaOH 100%
5.0 0.10 08 Formaldehyde 37% 105.5 1.04 09 NaOH 100% 2.5 0.05 10
NaOH 100% 2.5 0.05 Total 1536.7
[0156] In Stage 1, water was combined with NaOH and ethylene glycol
with mixing. The mixture was heated to 70.degree. C. with modest
agitation. Soy flour was added to the mixture at 5% of the total
soy flour per minute with rapid stirring. The mixture was heated to
90.degree. C. over 15 minutes, and maintained at a temperature of
88-92.degree. C. for 1 hour.
[0157] In Stage 2, the mixture was removed from the heat source and
charged with formaldehyde over 10 minutes, then the solution was
maintained at 75.degree. C. for 20 minutes. Phenol was added to the
mixture over 10 minutes, and then NaOH was added. The solution was
heated to 75.degree. C., and formaldehyde was added over 10 minutes
while maintaining the temperature at 75.degree. C. NaOH was then
added, and the mixture held at 75.degree. C. for 5 minutes, then
the remaining NaOH was added. After maintaining the mixture at
75.degree. C. for an additional 90 minutes, it was cooled to
40.degree. C. in a cold water bath over 10-15 minutes. The solution
was filtered through a coarse screen.
Example 8
[0158] A reactive phenol formaldehyde was prepared by combining
components in the order as listed in Table 8. The reactive resin
was later blended with a soy phenol formaldehyde resin.
8TABLE 8 Sequence Ingredient Amount (g) Moles to Phenol 01 Water
94.5 02 NaOH 100% 23.3 0.20 03 Phenol 100% 274.4 1.00 04
Formaldehyde 37% 492.2 2.08 Total 884.4
[0159] Water was combined with NaOH and phenol and the mixture was
heated to 70.degree. C. Formaldehyde was then added dropwise over
60 minutes while maintaining the mixture at a temperature of
68-72.degree. C. The resulting clear homogeneous solution was held
at 70.degree. C. for 1 hour after the formaldehyde addition was
completed. The temperature was then raised to 85.degree. C. and
held at that temperature until a Gardner viscosity of "T" was
obtained (a total of 140 minutes). The mixture was then cooled to
40.degree. C. in a cold water bath over 10-15 minutes. The solution
was filtered through a coarse screen.
Example 9
[0160] A 70/30 phenol formaldehyde soy resin with 18% low molecular
weight phenol formaldehyde was prepared by combining 114.6 g of the
resin of Example 8 with 100 g of the resin of Example 7 to yield
214.6 g of a homogenous resin mixture.
[0161] A 70/30 phenol formaldehyde soy resin with 43% low molecular
weight phenol formaldehyde was prepared by combining 58.8 g of the
resin of Example 8 with 100 g of the resin of Example 5 to yield
158.8 g of a homogenous resin mixture.
Example 11
[0162] A 60/40 phenol formaldehyde soy resin with 35% low molecular
weight phenol formaldehyde was prepared by combining 103.2 g of the
resin of Example 8 with 196.8 g of the resin of Example 6 to yield
300.0 g of a homogenous resin mixture.
Example 12
[0163] A 60/40 phenol formaldehyde soy resin with 35% low molecular
weight phenol formaldehyde was prepared by combining 137.6 g of the
resin of Example 8 with 262.5 g of the resin of Example 6 and 14.0
g of 50% NaOH to yield 414.1 g of a homogenous resin mixture. The
additional NaOH increased the solids and reduced the viscosity of
the resulting mixture.
Example 13
[0164] A resin was prepared by combining components in the order as
listed in Table 9 to yield a 40/60 phenol formaldehyde soy resin
with 25% low molecular weight phenol formaldehyde in a one-pot
process.
9TABLE 9 Stage I Sequence Ingredient Amount (g) % to Soy 01 Water
269.2 02 NaOH 100% 10.0 8.0 03 Ethylene Glycol 1.9 1.5 04 Soy Flour
125.0 Stage II Sequence Ingredient Amount (g) Moles to Phenol 05
Formaldehyde 37% 65.2 0.62 06 Phenol 100% 91.4 0.75 07 NaOH 100%
6.7 0.13 08 Formaldehyde 37% 130.4 1.24 09 NaOH 100% 3.4 0.07 10
Phenol 100% 30.5 0.25 11 Formaldehyde 37% 65.2 0.62 12 NaOH 100%
3.4 0.07 Total 802.3
[0165] In Stage 1, water was combined with NaOH and ethylene glycol
with mixing. The mixture was heated to 70.degree. C. with modest
agitation. Soy flour was added to the mixture at 5% of the total
soy flour per minute with rapid stirring. The mixture was heated to
90.degree. C. over 15 minutes, and maintained at a temperature of
88-92.degree. C. for 1 hour.
[0166] In Stage 2, the mixture was removed from the heat source and
charged with formaldehyde over 5 minutes, then the solution was
maintained at 75.degree. C. for 60 minutes. Phenol was added to the
mixture over 5 minutes, and then NaOH was added. The solution was
heated to 75.degree. C. and maintained at that temperature for 30
minutes. Formaldehyde was added over 10 minutes while maintaining
the temperature at 75.degree. C. NaOH was then added, and the
mixture was heated to 90.degree. C. over 10 minutes. The mixture
was cooled to 75.degree. C. over 10 minutes, and then phenol was
added over 5 minutes while maintaining the temperature at
75.degree. C. Formaldehyde was then added over 5 minutes, after
which NaOH was added, all while maintaining the temperature at
75.degree. C. After maintaining the mixture at 75.degree. C. for an
additional 90 minutes, it was cooled to 40.degree. C. in a cold
water bath over 10-15 minutes. The solution was filtered through a
coarse screen.
Example 14
[0167] A resin was prepared by combining 655.8 g of the resin of
Example 13 with 92.6 g water and 24.1 g NaOH 50%. The resulting
resin exhibited a higher pH and a lower solids content and
viscosity than the resin of Example 13.
Example 15
[0168] A 50/50 phenol formaldehyde soy resin with 43% low molecular
weight phenol formaldehyde was prepared by combining 75.6 g of the
resin of Example 8 with 220.0 g of the resin of Example 7 to yield
295.6 g of a homogenous resin mixture.
Example 16
[0169] A 50/50 phenol formaldehyde soy resin with 43% low molecular
weight phenol formaldehyde modified with urea was prepared. 4.0 g
of urea was dissolved into 90.2 g of the resin of Example 8. The
resulting mixture was combined with 300.0 g of the resin of Example
7 to yield 394.2 g of a homogenous solution. The total urea to high
molecular weight phenol formaldehyde was 10% on a solids basis.
[0170] The properties of the resins of Examples 1-16 are summarized
in Table 10. The % Soy was calculated as follows: 1 Dry Soy ( g )
Dry Soy ( g ) + Cured Phenol Formaldehyde ( g ) .times. 100 = %
Soy
[0171] Viscosity was measured using a Brookfield Viscometer with
LVT#3 spindle at 60 and 30 RPMs. Solids were determined using a
150.degree. C./1 hour oven solids pan method. Gel times were
measured using a Sunshine gel meter at 98-100.degree. C. Extract
was measured as the amount of resin extracted from a cured oven
solids sample after 24 hour Soxhlet water extraction. Free phenol
was measured using High Pressure Liquid Chromatography (HPLC) with
3-hydroxymethyl phenol as an internal standard. Free formaldehyde
was determined using a hydroxylamine hydrochloride back titration
method.
10TABLE 10 Properties of Soy-Based Resins Viscosity Gel Time
Extract Free Phenol Free CH.sub.2O Example % Soy pH Solids (%)
(cps) (min) (%) (%) (%) Conventional 0 11.00 53.8 184/184 24.6 29.1
0.23 <0.1 Phenol Formaldehyde 8 0 10.30 44.9 760/760 23.0 2.8
0.52 0.70 (Phenol Formaldehyde - No Protein) 1 63 9.68 43.7
5100/6500 -- 20.0 -- -- (Comparative) 2 30 9.92 39 96/105 60.3 10.3
-- -- 3 40 9.90 38.9 218/245 -- 14.3 1.43 -- 4 40 9.96 38.4 70/72
55.2 12.9 2.33 0.22 5 50 10.00 39.6 714/848 54.3 13.0 -- -- 6 66
10.32 36.3 1080/1372 58.9 31.4 0.17 0.65 7 70 10.19 36.1 3880/4920
83.0 34.0 2.40 0.15 9 30 10.11 36.3 508/544 28.0 11.0 -- -- 10 30
10.05 41.2 638/676 35.5 -- -- -- 11 40 10.18 39.1 1150/1256 -- 16.6
-- -- 12 40 11.10 39.2 786/876 48.0 22.4 -- -- 13 40 10.12 --
>5000 -- -- -- -- 14 40 11.36 34.4 1190/1304 36.9 23.0 0.32 --
15 50 10.19 38.5 1852/2116 36.3 11.0 -- -- 16 50 10.29 38.3
3230/3780 42.3 20.5 -- --
Examples 17-34
[0172] Randomly oriented strand boards were prepared using the
resins of Examples 1-16. The panels were prepared to the
specifications of Table 11, unless otherwise indicated. In a
typical oriented strandboard method, sandwich board was prepared
with two face layers and one center core layer. The center core
layer represented 45% of the total dry mass of the finished panel.
The two outer face layers were of identical size and together
comprised the remaining 55% of the total mass. Unless otherwise
specified, the core section of all panels contained only commercial
phenol formaldehyde resin and commercial wax emulsion.
[0173] Two panels were prepared for each resin system under each
press time. The panels were measured for density, dry internal bond
(ASTM D-1037-99, four samples per panel), 24 hour room temperature
thickness swell (ASTM D-1037-99, two samples per panel), 2 hour
boil thickness swell (sample measurement and testing per ASTM
D-1037-99, two samples per panel), and wet internal bond (testing
per ASTM D-1037-99, two samples per panel). The lower the thickness
swell and the higher the internal bond strength (IB), the better
the performance of the adhesive. For comparison, all board sets
contained panels made from a commercial phenol formaldehyde resin
that were prepared using the same pressing cycle and furnish as the
soy based resins.
11 TABLE 11 Formed Mat Size: 16" .times. 16" Trimmed Board Size 14"
.times. 14" Furnish Moisture % 5.6 Furnish Type Mixed hard/soft
Face/Core Ratio 55/45 Final Thickness {fraction (7/16)}" Final
Target Density (lb/ft.sup.3) 42.0 Face Resin % 3.26 Face Wax
(emulsion) % 1.31 Core Resin % 3.89 (commercial phenol formaldehyde
control unless specified) Core Wax (emulsion) % 1.39 Press Size 20"
.times. 20" Press Temp (.degree. C.) 200 Press Soak Times (sec)
120-330 seconds as specified Press Close Time (sec) 40-50 Total
Face Matt Moisture (%) 11.0
[0174] The strand board panels of Examples 17-20 included woods
comprising 62% black tupelo, 34% soft maple, 3% yellow pine, and 1%
other species. The properties of the strand board panels are
summarized in Table 12.
12TABLE 12 Properties of Strand Board Panels Thickness Swell % 2 hr
Boil 24 hr Room Internal Bond (PSI) Press Soak Density at
100.degree. C. Temperature Dry Wet Ex. Face Resin % Soy (sec)
(lb/ft.sup.3) (one SD) (one SD) (one SD) (one SD) 17 Conventional 0
210 41.7 76.7 17.0 99.8 2.5 Phenol Formaldehyde (2.8) (1.9) (24.1)
(2.2) 330 42.3 62.8 15.2 86.3 8.1 (4.8) (1.5) (25.6) (1.5) 18 Ex. 3
40 210 41.6 84.4 20.8 72.4 0.6 (13.2) (1.9) (13.7) (0.5) 330 41.9
65.1 14.5 89.3 8.7 (3.6) (1.7) (16.5) (5.8) 19 Ex. 4 40 210 40.6
88.7 38.3 60.7 0.5 (6.9) (5.8) (16.6) (0.2) 330 40.6 65.9 15.3 97.8
2.1 (9.2) (2.2) (19.1) (1.3) 20 Ex. 3* 40 210 39.4 98.6 64.7 7.4
0.3 (15.0) (5.9) (1.4) 330 40.8 90.4 16.2 53.8 0.8 (8.6) (7.9)
(8.4) (0.4) *Resin was used in both face and core sections SD =
Standard Deviation
[0175] The results of Table 12 demonstrate that a composite panel
prepared from a soy flour based resin (for example, Example 18
prepared from a resin containing 40% soy flour) exhibited
comparable performance to that of a panel prepared from a
conventional phenol formaldehyde resin (Example 17). The soy flour
resin was also comparable to a similarly prepared soy isolate-based
resin (Example 19). Although soy based resins are particularly well
suited to use as a face resin, the data of Example 20 demonstrate
the suitability of a 40% soy flour based resin for use in both the
face and core sections of a composite panel when extended press
times are employed.
[0176] The strand board panels of Examples 21-29 included woods
comprising 26% black tupelo, 18% soft maple, 52% yellow pine and 4%
other species. The properties of the strand board panels are
summarized in Table 13.
13 TABLE 13 Thickness Swell % 2 hr Boil 24 hr Room Internal Bond
(PSI) Press Soak Density at 100.degree. C. Temperature Dry Wet Ex.
Face Resin % Soy (sec) (lb/ft.sup.3) (one SD) (one SD) (one SD)
(one SD) 21 Conventional 0 210 41.9 54.2 41.9 87.0 15.4 Phenol
Formaldehyde (2.5) (1.9) (14.4) (1.4) 330 41.6 48.3 37.3 87.8 14.4
(1.8) (1.2) (15.3) (5.5) 22 Ex. 8 0 210 42.2 60.2 42.7 92.3 14.3
(1.8) (3.3) (17.8) (2.0) 330 41.1 54.2 39.4 103.0 15.4 (3.0) (1.4)
(9.5) (2.4) 23 Ex. 5 50 210 41.6 83.1 52.9 70.6 0.3 (4.2) (4.8)
(15.5) 330 41.0 61.8 45.1 82.5 4.1 (2.1) (2.3) (15.8) (2.2) 24 Ex.
15 50 210 40.9 68.3 44.2 78.1 2.4 (4.6) (2.3) (3.9) (2.0) 330 40.3
57.2 40.2 90.3 7.6 (6.1) (2.3) (13.8) (2.3) 25 Ex. 2 30 210 42.0
58.5 41.8 88.0 10.9 (5.1) (1.2) (25.3) (3.6) 330 41.2 50.8 37.8
95.7 17.0 (1.6) (1.3) (19.6) (3.0) 26 Ex. 10 30 210 40.0 55.4 37.1
70.5 8.1 (1.3) (3.0) (27.3) (1.3) 330 40.5 47.1 34.7 101.7 15.0
(1.3) (2.4) (11.9) (3.0) 27 Ex. 9 30 210 40.7 52.4 39.3 83.4 16.7
(7.0) (3.8) (19.5) (6.5) 330 40.9 47.8 35.2 99.3 23.6 (4.4) (1.0)
(9.2) (3.4) 28 Ex. 7 70 210 40.0 75.3 56.1 40.6 0.3 (5.5) (6.2)
(8.8) 330 42.0 81.2 56.9 77.5 0.3 (6.0) (2.0) (13.7) 29 Ex. 16 50
210 41.9 70.9 47.8 78.8 2.4 (5.2) (2.7) (8.2) (2.3) 330 40.7 55.0
39.4 92.4 9.8 (6.4) (3.4) (10.1) (1.6) SD = Standard Deviation
[0177] The molecular weight of the crosslinking copolymer and the
amount of total soy in the soy-based resin were both factors
evaluated in the experiments reported in Table 13. The addition of
higher molecular weight phenol formaldehyde to a partially
copolymerized soy and low molecular weight phenol formaldehyde
resin yielded superior resins with faster cure speeds. As
demonstrated by the data of Examples 23 and 24, the higher soy
containing resins exhibited improved performance. The high
molecular weight phenol formaldehyde resin used was prepared
according to Example 8, and when used in the face section of the
composite panels performed comparably to the commercial phenol
formaldehyde control. (Example 21 compared to Example 22). Example
29 demonstrated that urea can be added to a high soy containing
resin with no adverse performance effects.
[0178] The strand board panels of Examples 30-34 included woods
comprising 4.2% black tupelo, 2.0% soft maple, 92.8% yellow pine,
and 1% other species. The properties of the strand board panels are
summarized in Table 14.
14 TABLE 14 Thickness Swell % 2 hr Boil 24 hr Room Internal Bond
(PSI) Press Soak Density at 100.degree. C. Temperature Dry Wet Ex.
Face Resin % Soy (sec) (lb/ft.sup.3) (one SD) (one SD) (one SD)
(one SD) 30 Conventional 0 150 42.1 68.1 42.5 53.3 3.6 Phenol
Formaldehyde (7.5) (4.2) (12.7) (1.7) 210 42.0 63.5 41.0 80.4 9.2
(6.0) (3.3) (7.7) (4.7) 31 Ex. 1 63 150 43.8 106.0 74.8 51.0 <1
(16.0) (5.7) (17.2) -- 210 42.9 106.1 64.9 44.9 <1 (14.8) (5.8)
(11.3) -- 32 Ex. 11 40 150 41.7 68.9 44.3 62.0 5.4 (6.6) (4.9)
(13.6) (4.5) 210 43.0 71.5 39.4 76.1 6.8 (3.3) (4.1) (12.8) (1.3)
33 Ex. 12 40 150 40.7 73.7 42.1 59.7 2.1 (7.4) (2.0) (15.9) (1.9)
210 42.4 62.4 40.3 75.8 9.2 (5.0) (2.8) (12.5) (5.4) 34 Ex. 14 40
150 42.3 68.5 43.2 80.2 7.4 (5.3) (3.8) (8.4) (2.9) 210 43.0 64.6
43.4 94.7 9.3 (6.0) (2.5) (17.6) (1.2) SD = Standard Deviation
[0179] Example 31 is a comparative example of a soy flour based
resin. Examples 32 and 33 demonstrate that a decrease in the
viscosity of the resin by the addition of more alkali can be
achieved and still yield a composite panel comparable to the
control. As demonstrated in Table 13, the addition of higher
molecular weight phenol formaldehyde to the soy flour and low
molecular phenol formaldehyde resin weight system resulted in
improved performance. The data of Table 14 demonstrated that
addition by either blending (Examples 32 or 33) or preparation in
situ in a one-pot process (Example 34) resulted in similar
performance.
Example 35
[0180] Soy-based dispersion resins were prepared according to the
following procedure. A soy-based adhesive prepared according to the
preferred embodiments was heated to a temperature of 20-30.degree.
C. Concentrated sulfuric acid was added dropwise to the rapidly
stirring adhesive solution until the target pH was obtained. The
resulting dispersion was then ready for use as an adhesive. Table
15 provides data on the properties of several adhesive dispersions.
The dispersions were prepared from an adhesive prepared according
to Example 36.
Example 36
[0181] A resin was prepared by combining components in the order as
listed in Table 15 to yield a 66/34 phenol formaldehyde soy resin
with 100% low molecular weight phenol formaldehyde.
15TABLE 15 Stage I Sequence Ingredient Amount (g) % to Soy 01 Water
285.9 02 NaOH 100% 12.0 8.0 03 Ethylene Glycol 2.25 1.5 04 Soy
Flour 150 Stage II Sequence Ingredient Amount (g) Moles to Phenol
05 Formaldehyde 37% 48.9 1.29 06 Phenol 100% 44.1 1.00 07 NaOH 100%
3.75 0.20 08 Formaldehyde 37% 80.4 2.11 09 NaOH 100% 1.9 0.10 10
NaOH 100% 1.9 0.10 Total 631.1
[0182] In Stage 1, water was combined with NaOH and ethylene glycol
with mixing. The mixture was heated to 70.degree. C. with modest
agitation. Soy flour was added to the mixture at 5% of the total
soy flour per minute with rapid stirring. The mixture was heated to
90.degree. C. over 15 minutes, and maintained at a temperature of
88-92.degree. C. for 1 hour.
[0183] In Stage 2, the mixture was removed from the heat source and
charged with formaldehyde over 5 minutes, while maintaining
90.degree. C. for an additional 55 minutes after the addition was
complete. Phenol was added to the mixture over 10 minutes and the
solution was cooled to 75.degree. C., then NaOH was added.
Formaldehyde was added over 10 minutes while maintaining the
temperature at 75.degree. C. NaOH was then added, and the mixture
held at 75.degree. C. for 5 minutes, then the remaining NaOH was
added. After maintaining the mixture at 75.degree. C. for an
additional 90 minutes, it was cooled to 40.degree. C. in a cold
water bath over 10-15 minutes. The solution was filtered through a
coarse screen.
Example 37
[0184] A reactive phenol formaldehyde was prepared by combining
components in the order as listed in Table 16.
16TABLE 16 Sequence Ingredient Amount (g) Moles to Phenol 01 Water
94.5 02 NaOH 100% 23.3 0.20 03 Phenol 100% 274.4 1.00 04
Formaldehyde 37% 492.2 2.08 Total 884.4
[0185] Water was combined with NaOH and phenol and the mixture was
heated to 70.degree. C. Formaldehyde was then added dropwise over
60 minutes while maintaining the mixture at a temperature of
68-72.degree. C. The resulting clear homogeneous solution was held
at 70.degree. C. for 1 hour after the formaldehyde addition was
completed. The temperature was then raised to 85.degree. C. and
held at that temperature until a Gardner viscosity of "T" was
obtained (a total of 140 minutes). The mixture was then cooled to
40.degree. C. in a cold water bath over 10-15 minutes. The solution
was filtered through a coarse screen.
Example 38
[0186] A dispersion resin was prepared by combining components in
the order as listed in Table 17 to yield a 34/66 phenol
formaldehyde soy resin.
17TABLE 17 Sequence Ingredient Amount (g) 01 Resin from Example 36
400.0 02 Sulfuric Acid 14.0 Total 414.0
[0187] To a 1 liter round bottom flask equipped with an overhead
stirrer, thermometer, and condenser, the resin from Example 36 was
charged and the agitation was then initiated. The resin solution
was allowed to stir for 5 minutes while the temperature was
adjusted to 25.degree. C. with a water bath. The condenser was then
removed from the flask and the sulfuric acid was added dropwise to
the rapidly stirring mixture over a period of 5 minutes. The
exotherm was controlled with a water bath and the max temperature
was 29.degree. C. The dispersion was allowed to mix for 10 minutes
at a temperature of 25.degree. C. The dispersion was filtered
through a coarse screen.
Example 39
[0188] A dispersion resin was prepared by combining components in
the order as listed in Table 18 to yield a 34/66 phenol
formaldehyde soy resin. The molecular weight of the resin was
increased by further heating after the inversion process.
18TABLE 18 Sequence Ingredient Amount (g) 01 Resin from Example 36
400.0 02 Sulfuric Acid 14.0 Total 414.0
[0189] To a 1 liter round bottom flask equipped with an overhead
stirrer, thermometer, and condenser, the resin from Example 36 was
charged and the agitation was then initiated. The temperature of
the resin solution was then raised to 85.degree. C. over 30 minutes
and held for 1 hr at 85.degree. C. and then cooled to 25.degree. C.
with an ice water bath. The condenser was then removed from the
flask and the sulfuric acid was added dropwise to the rapidly
stirring mixture over a period of 10 minutes. The dispersion was
allowed to mix for 20 minutes at a temperature of 25.degree. C. The
dispersion was filtered through a coarse screen.
Example 40
[0190] A dispersion resin was prepared by combining components in
the order as listed in Table 19 to yield a 50/50 phenol
formaldehyde soy resin.
19TABLE 19 Sequence Ingredient Amount (g) 01 Resin from Example 36
814.8 02 Resin from Example 37 191.5 03 Sulfuric Acid 35.2 Total
1041.5
[0191] To a 2 liter round bottom flask equipped with an overhead
stirrer, thermometer, and condenser, the resin from Example 36 was
charged and the agitation was then started. The resin from Example
37 was then added and the mixture was allowed to stir for 5 minutes
while the temperature was adjusted to 23.degree. C. with a water
bath. The condenser was then removed from the flask and the
sulfuric acid was added dropwise to the rapidly stirring mixture
over a period of 10 minutes. The dispersion was allowed to mix for
15 minutes at a temperature of 25.degree. C. The dispersion was
filtered through a coarse screen.
Example 41
[0192] A dispersion resin was prepared by combining components in
the order as listed in Table 20 to yield a 50/50 phenol
formaldehyde soy resin similar to Example 40, but with a lower
pH.
20TABLE 20 Sequence Ingredient Amount (g) 01 Resin from Example 40
455.1 02 Sulfuric Acid 6.8 Total 461.9
[0193] To a round bottom flask equipped with an overhead stirrer,
thermometer, and condenser, the resin from Example 40 was charged
and the agitation was then started. The mixture was allowed to stir
for 5 minutes while the temperature was adjusted to 25.degree. C.
with a water bath. The condenser was then removed from the flask
and the sulfuric acid was added dropwise to the rapidly stirring
mixture over a period of 5 minutes. The dispersion was allowed to
mix for 15 minutes at a temperature of 25.degree. C. The dispersion
was filtered through a coarse screen.
Example 42
[0194] Soy dispersions were combined with isocyanate resins to
improve their durability. The lower pH of the dispersion, compared
to typical alkaline phenol formaldehyde resins, renders it
compatible with isocyanate resins. In this example, a dispersion
resin, similar to that in Example 38 was combined with commercial
polymerized methylene diisocyanate (pMDI). A dispersion resin was
prepared by combining components in the order as listed in Table 21
to yield a 60/31/9 Soy/phenol formaldehyde/pMDI soy resin.
21TABLE 21 Sequence Ingredient Amount (g) 01 Resin from Example 38
500.0 02 PMDI 17.3 Total 517.3
[0195] To a round bottom flask equipped with an overhead stirrer,
thermometer, and condenser, the resin from Example 38 was charged
and the agitation was then started. The mixture was allowed to stir
for 5 minutes while the temperature was adjusted to 25.degree. C.
with a water bath. The condenser was then removed from the flask
and the pMDI was added dropwise to the rapidly stirring mixture
over a period of 5 minutes. The dispersion was allowed to mix for
15 minutes at a temperature of 25.degree. C. The dispersion was
filtered through a coarse screen.
Example 43
[0196] Soy dispersions were prepared with urea formaldehyde (UF)
resins prepared in situ. The lower pH of the dispersion, compared
to typical alkaline phenol formaldehyde resins, renders it reactive
with UF resins. In this example, an alkaline soy-PF resin was
prepared first, followed by the addition of urea, inversion and
additional formaldehyde. The dispersion resin was prepared by
combining components in the order as listed in Table 22 to yield a
50/25/25 Soy/phenol formaldehyde/urea formaldehyde resin with a
total formaldehyde/phenol plus urea of 1.95 moles/moles.
22TABLE 22 Stage I Sequence Ingredient Amount (g) % to Soy 01 Water
522.1 02 NaOH 100% 25.0 10.0 03 Ethylene Glycol 3.75 1.5 04 Dow
Antifoam 1500 0.25 0.1 05 Soy Flour 250.0 Stage II Sequence
Ingredient Amount (g) Moles to Phenol 06 Formaldehyde 37% 85.1 1.26
07 Phenol 100% 78.2 1.00 08 NaOH 100% 10.0 0.40 09 Formaldehyde 37%
252.0 3.74 10 NaOH 100% 5.0 0.20 11 NaOH 100% 5.0 0.20 12 Urea 78.2
1.57 Total 1314.6
[0197] In Stage 1, water was combined with NaOH, ethylene glycol
and Dow Antifoam 1500 with mixing. The mixture was heated to
70.degree. C. with modest agitation. Soy flour was added to the
mixture at 5% of the total soy flour per minute with rapid
stirring. The mixture was heated to 90.degree. C. over 15 minutes,
and maintained at a temperature of 88-92.degree. C. for 1 hour.
[0198] In Stage 2, the mixture was removed from the heat source and
charged with formaldehyde (06) over 5 minutes, while maintaining
90.degree. C. for an additional 55 minutes after the addition was
complete. Phenol (07) was added to the mixture over 10 minutes and
the solution was cooled to 75 C., then NaOH (08) was added.
Formaldehyde (09) was added over 10 minutes while maintaining the
temperature at 75.degree. C. NaOH (10) was then added, and the
mixture held at 75.degree. C. for 5 minutes, then the remaining
NaOH (11) was added. After maintaining the mixture at 75.degree. C.
for an additional 90 minutes, urea (12) was added over 5 minutes
and the temperature was maintained at 75.degree. C. for 90 minutes.
The solution was then cooled to 40.degree. C. in a cold water bath
over 10-15 minutes and was filtered through a coarse screen
Example 44
[0199] A dispersion resin was prepared from the resin in Example 43
followed by the addition of extra formaldehyde, resulting in a
total molar ratio of formaldehyde/phenol plus urea level of 2.72.
This was done by combining components in the order as listed in
Table 23 to yield a 50/25/25 Soy/PF/UF resin.
23TABLE 23 Sequence Ingredient Amount (g) 01 Resin from Example 43
263.8 02 Sulfuric Acid 11.2 03 Formaldehyde 37% 22.0 Total
[0200] To a 1 liter round bottom flask equipped with an overhead
stirrer, thermometer, and condenser, the resin from Example 43 was
charged and the agitation was then initiated. The resin solution
was allowed to stir for 5 minutes while the temperature was
adjusted to 25.degree. C. with a water bath. The condenser was then
removed from the flask and the sulfuric acid was added dropwise to
the rapidly stirring mixture over a period of 5 minutes. The
exotherm was controlled with a water bath and the max temperature
was 29.degree. C. The dispersion was allowed to mix for 15 minutes
at a temperature of 25.degree. C. Formaldehyde (03) was charged
over 5 minutes to the rapidly stirring dispersion. The temperature
was increased to 75.degree. C. over 30 minutes and maintained for 1
hr. The dispersion was then filtered through a coarse screen.
[0201] As the data of Table 24 demonstrate, the acid dispersions
possess lower viscosity and lower resin extractables than the
corresponding adhesive from which the dispersion was prepared. The
data also demonstrate that higher soy contents can be employed
while maintaining acceptable properties of the adhesive
dispersion.
24TABLE 24 Properties of Soy-Based Alkaline Resins and Acid
Dispersions Free Solids Viscosity CH.sub.2O Extract Example % Soy
pH (%) (cps) (%) (%) Conventional 0 11.00 53.8 184/184 -- 29.1
Phenol Formaldehyde 36 66 10.27 34.9 1054/1296 -- 31.4 38 66 4.31
36.0 606/764 -- 30.9 39 66 4.27 36.0 1066/1444 -- -- 40 50 4.28
38.1 300/364 -- 23.0 41 50 2.35 38.2 320/376 -- -- 42 60 4.20 38.0
982/1236 -- 27.1 43 50 10.82 38.6 352/400 0.21 45.0 44 50 4.56 37.5
178/200 0.52 37.2
[0202] Viscosity was measured using a Brookfield Viscometer with
LVT#3 spindle at 60 and 30 RPMs, respectively. Solids were
determined using a 150.degree. C./1 hour oven solids pan method,
except for urea containing the adhesives of Example 43 and Example
44 where a 125.degree. C./90 min oven solids pan method was
employed. Gel times were measured using a Sunshine gel meter at
98-100.degree. C. Extract was measured as the amount of resin
extracted from a cured oven solids sample after 24 hour Soxhlet
water extraction
[0203] Randomly oriented strand boards were prepared using a
conventional phenol formaldehyde resin and the resins of Examples
36 through 42. The panels were prepared to the specifications of
Table 11, unless otherwise indicated. In a typical oriented
strandboard method, sandwich board is prepared with two face layers
and one center core layer. The center core layer represented 45% of
the total dry mass of the finished panel. The two outer face layers
were of identical size and together comprised the remaining 55% of
the total mass. Unless otherwise specified, the core section of all
panels contained only commercial phenol formaldehyde resin and
commercial wax emulsion.
[0204] Two panels were prepared for each resin system under each
press time. The panels were measured for density, dry internal bond
(ASTM D-1037-99, four samples per panel), 24 hour room temperature
thickness swell (ASTM D-1037-99, two samples per panel), 2 hour
boil thickness swell (sample measurement and testing per ASTM
D-1037-99, two samples per panel). The lower the thickness swell
and the higher the internal bond strength (IB), the better the
performance of the adhesive. For comparison, all board sets contain
panels made from a commercial phenol formaldehyde resin that was
prepared using the same pressing cycle and furnish as the soy based
resins.
25TABLE 25 Properties of Strand Board Panels Internal Thickness
Swell % Bond Ave Board 2 hr Boil 24 hr Room (PSI) Press Soak
Density Thickness at 100.degree. C. Temperature Dry Ex. Face Resin
% Soy (sec) (lb/ft.sup.3) (mm) (one SD) (one SD) one SD --
Conventional 150 40.2 10.89 56.6 33.5 83.7 Phenol Formaldehyde
(9.3) (4.5) (16.6) 45 Ex. 36 210 40.5 10.73 53.7 31.0 101.5 (8.1)
(2.9) (17.9) 46 Ex. 38 210 42.8 10.63 76.0 38.0 (9.9) (1.4) 330
42.5 10.57 60.6 33.7 (3.4) (2.3) 47 Ex. 39 210 41.9 10.76 68.0 40.0
105.4 (2.3) (1.7) (15.1) 330 42.0 10.69 65.6 38.6 89.3 (9.2) (2.4)
(30.5) 48 Ex. 40 210 43.4 10.63 64.6 38.1 95.4 (10.0) (0.7) (20.2)
330 42.8 10.62 55.6 33.6 89.1 (7.1) (2.6) (26.5) 49 Ex. 41 210 41.8
10.75 62.8 35.3 80.9 (13.8) (3.3) (14.0) 330 41.6 10.73 55.9 32.8
87.1 (10.6) (3.6) (15.8) 50 Ex 42 210 41.7 11.09 76.9 17.3 84.8
(6.4) (1.4) (11.1) 330 41.1 11.10 63.0 15.8 64.1 (8.6) (0.8)
(17.6)
[0205] The data of Table 25 demonstrated that a decrease in the
viscosity of the adhesive by the addition of acid to form a
dispersion can be achieved and still yield a composite panel
comparable to the control. Most notably, the excellent thickness
swell results even though the control phenol formaldehyde panel was
significantly lower in density. The data also demonstrated that
higher soy levels can be employed and still yield a composite panel
exhibiting satisfactory performance. The addition of 10% pMDI in
example 50 resulted in the panel with superior room temperature
thickness swell resistance.
[0206] Adhesives and methods of preparing and using same are
disclosed in co-pending U.S. application Ser. No. 10/211,944 filed
Aug. 1, 2002 and entitled "VEGETABLE PROTEIN ADHESIVE COMPOSITIONS"
and U.S. application Ser. No. 10/818,714 filed Apr. 5, 2004 and
entitled "WATER-RESISTANT VEGETABLE PROTEIN ADHESIVE
COMPOSITIONS."
[0207] All references cited herein, including but not limited to
published and unpublished applications, patents, and literature
references, are incorporated herein by reference in their entirety
and are hereby made a part of this specification. To the extent
publications and patents or patent applications incorporated by
reference contradict the disclosure contained in the specification,
the specification is intended to supersede and/or take precedence
over any such contradictory material.
[0208] The term "comprising" as used herein is synonymous with
"including," "containing," or "characterized by," and is inclusive
or open-ended and does not exclude additional, unrecited elements
or method steps.
[0209] All numbers expressing quantities of ingredients, reaction
conditions, and so forth used in the specification are to be
understood as being modified in all instances by the term "about."
Accordingly, unless indicated to the contrary, the numerical
parameters set forth herein are approximations that may vary
depending upon the desired properties sought to be obtained. At the
very least, and not as an attempt to limit the application of the
doctrine of equivalents to the scope of any claims in any
application claiming priority to the present application, each
numerical parameter should be construed in light of the number of
significant digits and ordinary rounding approaches.
[0210] The above description discloses several methods and
materials of the present invention. This invention is susceptible
to modifications in the methods and materials, as well as
alterations in the fabrication methods and equipment. Such
modifications will become apparent to those skilled in the art from
a consideration of this disclosure or practice of the invention
disclosed herein. Consequently, it is not intended that this
invention be limited to the specific embodiments disclosed herein,
but that it cover all modifications and alternatives coming within
the true scope and spirit of the invention.
* * * * *